We routinely get calls from customers who ask: “Which of your products is best for my oven temperature measurement application?” Whether you are an engineer planning for your next furnace temperature profiling project or a paint shop looking to monitor paint curing as part of quality assurance, the number of available options when choosing your oven temperature data logger can be overwhelming. Considering the wide variety of systems available today, making a call to an experienced solutions provider is the best way to get the information you need to make an informed decision. The majority of these calls get customers started with this simple response: “Sure, what are you looking to accomplish?”

So What Is Thermal Profiling?

Thermal profiling is the measurement of the temperatures throughout the interior of an oven. Essentially, there are two types of oven temperature profiling: through-process profiling and stationary or batch oven profiling.

Through-process profiling relates to tunnel or conveyor ovens, where the product moves through the oven as it is heated, while a batch oven is manually loaded and unloaded, and the product remains stationary throughout the process. A batch oven typically uses a fixed data logger external to the oven with temperature probes that extend inside, while the conveyor-based oven requires a data logger that can move with the product through the oven.

Through-process oven profiling is used to validate that the parts moving through the cure cycle—which may feature multiple temperature zones—are experiencing the time at specified temperatures throughout the process. This requires a high-temperature data logger as well as a protective thermal barrier enclosure to further insulate the electronic logger from the high temperatures.

What Temperature Profiling System is Right for Me?

When deciding on an oven temperature data logger, it helps to first consider not only your immediate but also your future requirements. Here are 6 essential factors you should consider when selecting a logger:

1. Input Channels: First and foremost, how many different points do you need to measure within or on the product going through the oven, and how many can you foresee needing down the road? Since data loggers are available in many different configurations and models, knowing what you need now and possibly in the future will have a significant impact on your choice.
2. Probe Type: Will you need to measure the air and surface temperatures of your parts? Answering this will dictate the type of probes that are required.
3. Sensor Type: What temperature range do you need to work with? Commonly used thermocouple types include J and K, but more exotic types may be required for very high temperature ovens or kilns.
4. Thermal Protection: If this is a through-process application, does the logger’s enclosure need a special phase change insert for extended operation at the oven temperature?
5. Software Features: How user-friendly is the software? Do you require specialized calculations, such as paint cure percentage? Will you need additional software features, such as data analysis and report printout?
6. Regulator Compliance: Do you require compliance with any specific regulations, such as AMS 2750 D?

Generally, an experienced provider will ask specific questions to help you determine which data loggers are the most suitable for your individual application, including how many inputs are required and what type of thermocouple is best; how much data needs to be stored; temperature limits of the enclosure; necessary software features such as analysis and curing calculations; and any other requirements the application might have. This initial exploratory phase is the best time to engage a representative in a question-and-answer session with a quick phone call or online chat.

Example of An Oven Temperature Logger Profiling Kit

As an example of a complete temperature profiling kit, CAS DataLoggers offers Grant Instruments’ latest version of the popular OMK610 data logger with many new features to assist in production quality control and to cut operating costs. The logger’s enhanced thermal barrier gives it maximum protection, available with an optional heat-absorbing insert. The kit meets paint manufacturers’ specified cure parameters by maintaining a specified level of cure, ensuring repeatable quality, maximizing oven usage and throughput, and optimizing oven running (energy) costs. Additionally, the logger archives data and results as part of any quality control system or supplier audit trail, and line operators can use it without the need for a PC.

Equally deserving of consideration is the software your logger uses—most importantly, its ease of use, features, and cost. Grant’s easily programmable PaintView set-up and data analysis software offers % cure calculation, data storage, report generation, and analysis. PaintView also gives users a choice between using a ‘classic’ or ‘universal’ area integration cure analysis method. Users simply set the paint type and pick their cure method to get started logging. Also, unlike many competing software platforms, PaintView has no extra cost per installation.

You’ll want to closely examine what’s included with any temperature logging kit you’re considering. Grant’s complete OMK610 logger kit includes:

• The 6-channel OQ610 temperature data logger (for use with Type-K or T thermocouple probes)
• A thermal barrier suitable for paint curing applications
• USB communication cable
• PaintView data storage and analysis software
• A quick start guide
• A set of batteries
• A convenient carrying case

Additionally, a thermal insert sleeve to extend the operating temperature range is also available, as well as your choice of fast response, high accuracy probes with models for air and surface temperature.

Given the amazing range of data logging products on the market, before you make your choice of manufacturer and model, make sure you speak with a trusted solutions provider to find out how to get the most suitable device for your specific application at the most affordable price. A good provider can offer you experienced help over the phone as well as live chat support and a detailed online store listing specifications. Make sure your provider also offers critical value-added services such as customization, configuration, and experienced technical support.

View more information on our Oven Temperature Logger Products.

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We live in an age of convenience, where a quick online search can yield seemingly endless options at incredibly low prices. Need a temperature sensor to monitor your freezer, a heated liquid holding tank, or for a renewable energy project? A no-name vendor might be tempting with their rock-bottom prices and promises of functionality. But before you click “Add to Cart,” let’s delve into the hidden costs of opting for the cheapest temperature sensors from unknown online sellers. Trust us, our experience from dealing with customers who made this choice is that the initial savings might end up costing you far more in the long run.

1. Accuracy – Do the Specs Leave You Guessing?

Temperature-sensitive applications demand accuracy. Whether you’re monitoring a vaccine storage refrigerator, beer fermentation vessels, or even just a saltwater aquarium, a reliable reading is paramount. Cheap, unbranded sensors often suffer from poor calibration and inconsistent performance. You might find yourself with readings that are significantly off, leading to:

• Spoiled Batches: In brewing or food processing, inaccurate temperature control can result in off-flavors, stalled fermentations, or even unsafe products.
• Compromised Environments: For aquariums or incubators, incorrect readings can stress or harm the inhabitants, leading to illness or even death.
• Flawed Data: In scientific experiments or data logging, unreliable sensors render your collected information useless.

Example: Imagine thinking your vaccine refrigerator is holding at the desired 36°F based on a cheap sensor, only to find out it’s actually at 32°F, causing the medication to freeze and be ruined.

2. Reliability – What’s the Cost of Failure?

Quality components and robust manufacturing processes cost money. Cheap sensors often utilize inferior materials and lack proper quality control. This translates to a higher likelihood of:

• Premature Failure: The sensor might stop working altogether after only a short period of use, forcing you to buy replacements frequently.
  Intermittent Issues: You might experience erratic readings, sudden spikes or drops, or periods where the sensor simply doesn’t report data. Troubleshooting these intermittent problems can be incredibly frustrating and time-consuming.
• Loose Connections and Poor Wiring: Low-quality soldering and flimsy wiring can lead to signal loss and unreliable data transmission.

Think about it: How much time and frustration will you waste replacing faulty sensors and debugging unreliable systems? The slightly higher cost of a reputable sensor quickly becomes negligible in comparison.

3. Lack of Documentation and Support:

When you buy from a reputable vendor, you usually get access to datasheets, calibration certificates, and technical support. If you encounter issues, you have someone to turn to for help. With no-name online sellers, you’re often on your own.

• Missing Datasheets: Without proper documentation, integrating the sensor into your project can be a nightmare. You might struggle to understand its specifications, wiring, or communication protocols.
• No Calibration Information: Knowing the sensor’s accuracy and having the ability to calibrate it is essential for many applications. Cheap sensors rarely come with this crucial information.
• Zero Customer Support: If your sensor malfunctions or you have questions, good luck getting any assistance from an anonymous online seller.

Consider This: Your project hits a snag, and you suspect the temperature sensor. Without any documentation or support, you could spend hours trying to diagnose the problem. In the end, was the couple of bucks you saved worth the time you lost trying to figure out why the data didn’t make sense?

4. Safety Concerns You Can’t Ignore:

In certain applications, especially those involving heating elements or critical environmental controls, a faulty temperature sensor can pose a safety risk.

• Overheating: An inaccurate sensor might fail to trigger safety mechanisms, leading to overheating, fire hazards, or damage to equipment.
• Incorrect Environmental Control: In medical or laboratory settings, unreliable sensors could lead to dangerous temperature fluctuations with serious consequences.

Ask Yourself: Is saving a few dollars worth jeopardizing safety and potentially causing significant damage?

5. Hidden Costs Beyond the Initial Price:

While the initial price tag might be appealing, the true cost of cheap sensors can be much higher:

• Increased Downtime: Frequent failures lead to disruptions in your processes or projects.
• Wasted Time and Effort: Troubleshooting unreliable sensors and implementing workarounds consumes valuable time.
• Cost of Replacements: Constantly buying new cheap sensors adds up over time.
• Potential Damage: Inaccurate readings can lead to spoiled materials, damaged equipment, or harm to living organisms.

The Takeaway:

While inexpensive temperature sensors may seem attractive, especially for DIY projects on a budget, it’s crucial to consider the potential long-term costs and risks. Investing in sensors from reputable vendors, even if they cost a bit more upfront, often guarantees better accuracy, reliability, documentation, and support. This ultimately saves you time, money, and potential headaches down the line.

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The Challenges Facing Museums:

A variety of environmental conditions can damage artwork, which museums need to actively monitor:

• • Temperature Fluctuations: Extreme temperatures can cause materials to expand, contract, or even crack. Sudden shifts are particularly damaging, especially for paintings and delicate artifacts.
  • Humidity Variations: High humidity can encourage mold growth on organic materials and corrosion on metals, while low humidity can cause fragile materials to become brittle and crack.
  • Light Exposure: Excessive light, particularly UV radiation, can fade colors, embrittle materials, and accelerate deterioration.
  • Pollution and Contaminants: Air pollutants can interact with materials, causing discoloration, corrosion, and other forms of damage. For example, ozone is known to be particularly damaging to pigments and dyes, causing color loss.
  • Moisture: In a worst-case scenario, a broken pipe or water intrusion from heavy rain or a flood can ruin items stored out of regular view before being detected.

The Role of Data Loggers in Environmental Monitoring:

Data loggers continuously monitor and record environmental parameters, providing both real-time insights and tracking long-term trends, plus offering immediate notification. In a museum setting, they play a crucial role by:

1. Providing Real-time Insights: Data loggers offer real-time readings of temperature, humidity, light levels, and other critical factors. This allows museum staff to proactively address any deviations from optimal conditions.
2. Generating Historical Data: By recording data over extended periods, data loggers provide valuable historical information about environmental conditions. This data can be used to identify long-term trends, assess the impact of past events, and refine environmental control strategies. Data loggers with the ability to track cumulative light exposure provide essential information to manage fragile paintings and documents.
3. Triggering Alarms: Data loggers can be configured to trigger alarms when conditions exceed predefined thresholds. This allows for immediate intervention to prevent damage to valuable artifacts in case of an equipment failure or other emergency.

Trending Data Logging Solutions:

The market for data loggers has experienced two significant trends in the past few years. First, wireless technology has become pervasive. Wireless data loggers eliminate the need for cumbersome wiring, making them easy to deploy in various locations within the museum. Compact, battery-powered devices can be easily and unobtrusively hidden within exhibits open to the public to provide monitoring. Second, data loggers that publish data to cloud-based platforms allow museum staff to remotely access data, monitor conditions in real time, and receive alerts via email or SMS. This enables proactive maintenance and reduces the risk of damage.

Conclusion:

Environmental monitoring is essential for the long-term preservation of museum collections. By leveraging the power of data loggers with real-time alarming and cloud-based data management, museums can proactively safeguard their invaluable assets, ensuring these treasures are enjoyed by generations to come.

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Achieving Regulatory Compliance and Patient Safety with Advanced Temperature Monitoring

The evolving needs of the healthcare industry demand a more sophisticated approach to temperature monitoring. Data loggers empower organizations to:

• Forge a Path to Compliance: Navigate the complex regulatory landscape with ease. Data loggers generate comprehensive, tamper-proof records that seamlessly demonstrate adherence to stringent FDA and other regulatory guidelines, minimizing the risk of costly non-compliance penalties.
• Prioritize Patient Well-being: Ensure the safety and efficacy of critical medical products. By continuously monitoring temperatures in blood banks, pharmacies, and vaccine storage facilities, data loggers mitigate the risk of product degradation, safeguarding patient health and well-being. Email, SMS, or voice alerts provide immediate notification before materials are compromised.
• Unlock Operational Efficiency: Streamline workflows and maximize resource utilization. Automated data collection eliminates the need for manual checks, freeing up valuable staff time for more critical tasks and improving overall operational efficiency.
• Provide Around-the-Clock Surveillance: Data loggers provide 24/7/365 monitoring and notification to cover nights, weekends, and holidays when staff may not be on-site to check local measurement devices.

Proactive Cold Chain Management: Predictive Insights and Data-Driven Decisions

• Predictive Insights for Proactive Action: Go beyond reactive measures. Analyze historical data to identify potential temperature excursions and equipment malfunctions before they occur. This proactive approach enables preemptive maintenance, minimizes disruptions, and enhances operational resilience. By analyzing historical data from data loggers, healthcare facilities can identify patterns and trends, allowing for preemptive maintenance and preventing costly product loss. For example, an increase in the variability or frequency of temperature fluctuations in a vaccine refrigerator can provide early indications of impending equipment failure.
• Data-Driven Decisions for Enhanced Performance: Leverage the power of data analytics to gain deeper insights into your cold chain processes. Identify areas for improvement, optimize storage conditions, and make data-driven decisions to enhance operational efficiency, reduce costs, and ultimately improve patient outcomes.
• A Foundation of Confidence: Instill confidence in your cold chain management practices. Data loggers provide irrefutable evidence of temperature compliance, enhancing trust with patients, regulators, and other stakeholders.

Build Trust Across the Entire Cold Chain

• Robust Alarms for Rapid Response: Receive immediate alerts via email, SMS, and phone when temperature excursions occur, enabling swift intervention and minimizing potential risks.
• Cloud-Based Solutions for Enhanced Accessibility: Access data remotely, generate reports effortlessly, and ensure data security and integrity with robust cloud-based platforms.
• FDA-Compliant Solutions for Peace of Mind: Select from a comprehensive range of FDA-compliant data loggers that meet the rigorous demands of the healthcare industry.

Conclusion

In the ever-evolving landscape of healthcare and life sciences, elevating temperature monitoring practices is not just an option – it’s a necessity. By embracing advanced data logging solutions, healthcare organizations can not only ensure the integrity of temperature-sensitive materials but also build a foundation of trust and operational excellence. Contact us today to learn how our FDA-compliant data loggers can transform your cold chain management.

The post Elevating Medical Temperature Monitoring: Data Loggers For Enhanced Quality & Confidence appeared first on CAS Dataloggers.

The Invisible Threat

Many foodborne illnesses, including those potentially linked to avian influenza, are invisible to the naked eye. Proper temperature control during transport, production, and storage—from the source to the point of consumption—is critical for preventing foodborne illness. Consuming undercooked poultry or beef, or unpasteurized (raw) milk, can have serious health consequences. Cooking poultry, eggs, and beef to the appropriate internal temperature kills bacteria and viruses, including avian influenza A viruses.

Automating Food Safety

Data loggers offer a powerful solution for automating food temperature monitoring. By continuously recording temperature data, these devices provide an invaluable record of food safety compliance. This is particularly critical in today’s complex food supply chains, where products may travel long distances and pass through multiple hands before reaching consumers. The CDC emphasizes the importance of using data loggers in refrigerators, freezers, and storage areas to monitor food temperatures and ensure compliance with regulations. Loggers are also used in food processing to monitor cooking, holding, and cool down to ensure items are adequately cooked or processed, held at a temperature above 140°F to inhibit the growth of harmful organisms or cooled rapidly to minimize the time any item remains within the critical temperature window of 140°F to 68°F.

Compliance And Confidence

With the new FDA Food Code rules, HACCP principles, and the FSMA, accurate food temperature monitoring is not just a best practice; it’s a legal requirement. Data loggers provide irrefutable evidence of compliance, giving food businesses confidence that they are meeting the highest standards of food safety.

Figure 1. Important Food Safety temperatures to know

A Multi-Layered Approach

Food monitoring data loggers are used for all phases of monitoring, including warehousing, refrigerated storage, transportation, cooking, and processing. This multi-layered approach ensures that food safety is maintained throughout the entire journey, from farm to fork.

Key Takeaways

• Data loggers play a crucial role in enhancing food safety, especially in light of high-profile outbreaks of illness related to vegetables, meats, and other products.
• By automating temperature monitoring, data loggers improve traceability, identify potential critical control points, and enable data-driven decision-making.
• The CDC recognizes the importance of using data loggers to monitor food temperatures in storage, transport, and production, emphasizing their role in preventing the spread of foodborne illnesses.

Investing in data loggers is not only a matter of food safety, but also a matter of ensuring compliance and maintaining consumer confidence.

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Selection Criteria

Picking which type of sensor to use for a particular application requires consideration of 3 important factors related to the measurement, along with the cost:

• Temperature Measurement Range
• Required Measurement Accuracy
• Sensor Wire Length, Noise, and Accuracy

One of the most important things is the expected temperature measurement range. Of the three types of sensors, thermocouples have the widest measurement range, from well below -200°C to over 1700°C depending on the thermocouple type. RTDs are more limited spanning -200C to around 500°C although specialized models can go somewhat higher. Thermistors have the most limited measurement range of the 3 types because of both their composition and their non-linear characteristics. Commonly available epoxy-coated thermistors are suitable for use from -50°C to 150°C and glass-coated thermistors can measure above 200°C.

A second consideration is the required accuracy of the temperature measurement. We usually tell customers that of the three types, thermocouples are the least accurate. Standard thermocouple wire is usually specified to have an accuracy of around 1 – 1.5°C based on the wire type and temperature. Small variations in the composition of the metal alloy making up the wire can affect the output voltage.

Some vendors provide thermocouple wire called special limit of error or SLE with a slightly better temperature specification. As mentioned before, thermocouples also require a second reference temperature measurement so any error in this measurement will enter directly into the total error. RTDs have accuracy specified in different classes; class A RTDs have an accuracy of around 0.15°C at 0°C, class B is 0.3°C and class AA or 1/3 DIN is about 0.1°C at the same temperature. So, overall RTDs are 5-10x more accurate than thermocouples. As mentioned before, thermistors exhibit a much greater change in resistance per degree C and so accuracies of 0.1°C are easily achievable.

In any real-world application, the environment where the sensor is installed and the distance between the sensor and the measuring device must be taken into account. I can’t tell you how many times we have received questions from customers about noisy thermocouple measurements. As mentioned before, thermocouples only generate a tiny voltage, on the order of millivolts. Any electromagnetic noise in the area where the thermocouple wires run can couple directly into the wire often completely swamping out the signal from the thermocouple. Things like AC power cables, large motors, or radio frequency (RF) equipment can ruin the measurements. In these cases, it becomes necessary to use shielded thermocouple wire or use a signal conditioner module to convert the low-level signal to something like a 4-20mA signal to get decent measurements.

Or, in the case of RTDs, as mentioned before they are typically a relatively low resistance (100 ohms) and an error of 1 ohm can represent an error of >2°C. Considering that 100 feet of standard 18 gauge wire will have a resistance of around 0.6 ohms it becomes apparent that using a 3 or 4 wire connection in combination with a measuring instrument that provides compensations is necessary for accurate measurements. However, there is normally an upper limit on how much lead resistance the measuring device can adjust for. We usually recommend that it’s best to keep RTD wire length to less than 50 feet. Thermistors used for temperature measurement are usually much higher in resistance than RTDs, 2252 and 10,000 ohms are common values so the impact of cable length is usually negligible.

Of course, any consideration of which type of sensor to use has to include the cost. Of the 3 types, thermocouples are probably the least expensive. Standard thermocouple wire can be purchased for less than $1.00/foot. Simply stripping the ends and twisting them together can produce a basic functional thermocouple. Also, when looking for probes, thermocouples are widely available in the largest range of styles from simple tubular probes to surface temperature probes to models that can be bolted onto a piece of equipment like a bearing. Both the RTD and thermistor sensing elements themselves can be a bit more expensive upwards of $15-20 for a good quality device. Normally these then need to pack into some type of probe to protect the sensing element so they will typically be a bit more expensive than the same style thermocouple probe.

Typical Examples

Here are a few common applications along with the sensor type that was used:

We have provided data loggers and sensors for several applications for skin temperature measurement. This is an ideal application for a thermistor sensor; the temperature measurement range is small typically only ± a few degrees and right in the sweet spot for thermistors measurements around 30°C and accuracy is very important, a few tenths of a degree can make a big difference. Fortunately, there are a few vendors that provide medically rated thermistor stick-on surface probes just for this application. When combined with one of our Grant Squirrel data loggers which offer built-in software for conversion of standard thermistor resistance to temperature they offer a very accurate and easy-to-use solution.

We offer data loggers for monitoring concrete curing where the temperature vs. time profile of poured concrete can be used as a good predictor of its maturity or strength. For this application, the sensor is embedded in the concrete and normally left in place after the test is complete. An accuracy of ± a degree is enough and while the sensor runs may be relatively long there is usually minimal electrical interference in the environment.

Which sensor type to use? You guessed it, thermocouples are the perfect solution. In this case, we provide a roll of thermocouple wire and the user can simply cut off the length needed, strip the ends, twist the wires together on one end, and attach the other to the data logger. Once the test is complete they cut off any wire sticking out of the concrete and can save it to reuse for the next test.

The last example is one of our biggest applications, monitoring the temperature in a medical refrigerator or freezer, for example, a refrigerator in a clinic used to hold vaccines. As dictated in the guidelines from the CDC for vaccine storage and the Vaccines For Children (VFC) program they recommend a digital data logger (DDL) with an uncertainty of ± 0.5°C (±1.0°F). This is a perfect application for a class A RTD probe which has an accuracy at least 2x better than the recommendation. Normally the logger is placed within 10 feet of the refrigerator so cable length is not an issue. When used with a data logger like our Accsense A2-05 it offers a complete, accurate solution for ensuring that vaccines or other medical supplies or samples have been stored properly.

Summary

Well, there you are. Selecting between a thermocouple, thermistor, or an RTD comes down to what temperature you will be measuring, the accuracy that you need, where you will be using the sensor, and how important the cost is vs. the performance. Hope you enjoyed this article and found it informative!

The post Thermocouple, Thermistor or RTD? – Part 2 appeared first on CAS Dataloggers.

Temperature is probably the most common parameter measured by our data loggers. Some devices like the TandD TR71A come bundled with general-purpose temperature sensors while other systems such as the dataTaker DT80 Universal Input data logger require the user to provide sensors. Also, some applications like monitoring the temperature of the fluid inside a pipe or tank require specialized temperature sensors to suit the physical requirements of getting the sensor in good thermal contact with what is to be measured. Now, there are quite a number of different kinds of devices that can provide an electrical output proportional to a temperature such as a thermocouple, resistance temperature detector (RTD), thermistors, and so on. Selecting the best sensor for a particular application requires looking at several different criteria and the tradeoffs between the different sensor types.

Basic Sensor Principles

In typical everyday applications, the most common sensor types are thermocouples, RTDs, and thermistors. In evaluating which to use, it is useful to understand how these devices convert temperature into an electrical signal that can be measured by a data logger.

Of all of the different types of temperature sensors, thermocouples are the most common. On the surface, the thermocouple is a very simple device; it consists of wires made from 2 different metal alloy wires that are twisted, welded, or fused together creating what is known as the junction. Thermocouples rely on the fact that whenever you have 2 different conductive materials in electrical contact with one another, a voltage will be created across the point where they are joined and this voltage will change as the temperature between the junction and the end of the wires changes. By closely controlling the composition of the 2 wires the voltage vs. temperature characteristic will follow a very well-defined characteristic defined in ITS-90.

There are 2 very important practical considerations of using thermocouples:

1. The voltage that is created is very small, typically in the range of -.01 to +.06 volts
2. The voltage is proportional to the difference in temperature between the junction and the ends of wires which requires a second independent temperature measurement at the point where the wires connect to the instrument called the reference junction temperature to derive the actual temperature at the junction.

RTDs operate on an entirely different principle, the change in resistance of a conductor (wire) with the change in temperature. For different types of metals, such as platinum, copper, or nickel, this change called the temperature coefficient of resistance is very consistent. Measurement of temperature with an RTD requires knowing the resistance of the RTD at 0°C, typically 100 ohms, measuring the resistance of the RTD, and then calculating its temperature by knowing the temperature coefficient. For example, a PT100 is a platinum RTD that measures 100 ohms at 0°C with a temperature coefficient of either .00385 ohms/degree (IEC/DIN standard) or .003902 ohms/degree (U.S. Industrial standard).

RTDs have an advantage over thermocouples in that the measurement is absolute, which is to say it does not depend on a second measurement like the thermocouple reference junction temperature. RTDs provide a more accurate measurement than thermocouples as defined by the class of the sensor. However, there are 2 important considerations when choosing RTDs.

First, they have a more limited temperature measurement range than thermocouples. Second, since the resistance is relatively low, typically 100 ohms, the resistance of the lead wires between the sensor and the measuring device can have a significant impact on the accuracy of the measurement. It’s for this reason that RTDs are often configured to use a 3 or 4-wire connection to improve the measurement accuracy.

The third common type of temperature sensor is thermistors which are a specialized type of electrical resistor, often a semiconducting material that has a non-linear relationship between temperature and resistance. Thermistors can have either a positive coefficient (PTC) where the resistance increases with increasing temperature or a negative coefficient (NTC) where the resistance change is in the opposite direction of temperature change – the resistance goes down as the temperature goes up. Whereas the resistance of an RTD might change by 0.3-0.4 ohms/°C the change in resistance of a thermistor can be 100 to 1000x greater, from 30 to > 400 ohms/°C.

Because the change in resistance is non-linear thermistors can have high accuracy but the tradeoff is that they normally have a more limited measurement range than RTD’s or thermocouples. Also, because the change is non-linear, the calculation of the temperature from the measured resistance is more complex although a linear approximation may be used over a limited temperature range.

The post Thermocouple, Thermistor or RTD? – Part 1 appeared first on CAS Dataloggers.

1. First, a thermocouple measures temperature by generating a very small voltage based on the temperature where the 2 wires are fused together at the tip or junction. For example, at a room temperature of 72°F, a type K thermocouple will output .000888 volts.
2. Second, the operation of the thermocouple is based on the Seebeck effect, where a conductor will generate a voltage differential across two points when there is a temperature difference between these points. This voltage is very dependent on the composition of the conductor; variations in the material will cause changes in the voltage vs. temperature characteristic.

These factors, when combined with the environment where the thermocouple will be used, directly affect the practical length of a run of thermocouple wire.

Is There Any Interference Nearby?

Probably the most important thing to consider is the effect of electrical and magnetic interference (EMI) in the environment when combined with the small output voltage of the thermocouple. One of the worst cases we ever ran into was a customer at a not-to-be-named nuclear power plant. He purchased one of our loggers to monitor the temperature inside a reactor room. After hooking up the thermocouples, he called us to say that the measurements were terrible. We were quite surprised because we had used these loggers in dozens of other applications with no problems. We dug a bit deeper and found out that the thermocouple wires were over a hundred feet long. Normally, this would not directly cause a problem, but in this case, the wires were running in conduit through the concrete wall of the reactor building alongside control and power cables. The thermocouple wires were picking up all sorts of electrical noise from the signals in these other cables, which was completely swamping out the signal for proper measurements.

So, when determining how far you can run the wires, it is essential to look at the area they will be going through and see if there are significant sources of electrical interference nearby. If so, you will have to keep the runs short or use twisted pair, shielded thermocouple wires, making sure that the shield is connected to good earth ground at only one end.

What Material Is Your Wire Made Of?

It’s also important to consider potential voltage drops across the length of the wire. Thermocouple wire is typically in the range of 18 to 24 gauge. For 24 gauge K-type wire, the resistance is about 1.5 ohms per foot for the pair. A 200-foot run would have a resistance of about 300 ohms, and when used with a typical data logger, this resistance could cause an error of nearly 0.5%. If you anticipate having to use a long run, consider using a larger diameter wire like 18 or 16 gauge to minimize resistance and voltage drop.

As noted above, the voltage created by a thermocouple is dependent on the temperature difference between the two ends of the wire and the material the wire is made of. The wire manufacturers do their best to maintain a consistent alloy throughout the wire, but even small variations in the alloy composition can have a big effect on the output voltage vs. temperature characteristic. Using very long runs increases the possibility of introducing material variations across the length of the wire. If you want to use a long length of wire, consider using wire with improved accuracy specifications, sometimes called “Special Limits of Error” or “SLE.” The extra cost may justify the improvement in measurement accuracy when making a long run.

Wrapping It All Up

So, what does this all really mean? Practically speaking, the longest you want to go with a standard thermocouple run is about 100 feet without having to start jumping through hoops to get an accurate, low-noise measurement. Even in this case, you will probably want to use shielded, SLE wire at least 18 gauge or larger. Just to be safe, we normally recommend a maximum of about 50 feet using regular thermocouples.

Now you may be saying to yourself, “OK, I still need to run 150 feet and I don’t want to go through all of this.” Well, the answer is actually pretty simple. We, along with many other vendors, offer thermocouple signal conditioners, such as the Novus TxBlock. These signal conditioners take the low-level millivolt output of the thermocouple and convert it to a high-level signal, like a 4-20 milliamp current that is much more suitable for running long distances. Using a signal conditioner like this has multiple benefits:

1. A high-level signal like a 4-20 mA current loop will be much more immune to the effects of EMI.
2. The effect of cable resistance will be eliminated as long as the power supply can drive the loop.
3. You can use lower-cost standard 2 conductor wire for the amplified signal instead of the more expensive shielded thermocouple wire.

As a comparison, 20 gauge, twisted pair, shielded K type thermocouple wire is about $1.41 per foot for a 500-foot roll while 2 conductor cables are $.14 per foot in the same size spool. The signal conditioner cost is a little over $50, so for anything over 45 feet, you will be ahead cost-wise using the regular wire and the TxBlock. Not to mention, you will have more accurate and lower noise measurements!

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With the approval and distribution of the Pfizer and Moderna COVID-19 vaccines, many clinics and pharmacies have begun their search for a solution to monitor vaccine temperature that meets the requirements of keeping the COVID-19 vaccines safe. According to the Center for Disease Control (CDC), the Moderna COVID-19 vaccine should be stored long-term in a freezer at a temperature between -25°C and -15°C (-13°F and 5°F) or in a refrigerator at a temperature between 2°C and 8°C (36°F and 46°F) for up to 30 days before the vaccine vial seal is punctured.

The Pfizer-BioNTech COVID-19 vaccine has slightly stricter requirements, needing an ultra-low freezer with temperatures between -80°C and -60°C (-112°F and -76°F) for long-term storage. The vaccine can be stored in a refrigerator prior to mixing for only 5 days (or 120 hours) at a temperature between 2°C and 8°C (36°F and 46°F). The Johnson & Johnson (Janssen) COVID-19 vaccine should be stored at a refrigerator temperature between 2°C and 8°C (36°F and 46°F) until its expiration or beyond use date and should not be placed in a freezer for storage. Once the Janssen vaccine vial is punctured, it must be held between 2°C and 8°C for up to 6 hours OR at room temperature (up to 25°C / 77°F) for up to 2 hours.

With these stringent requirements, the CDC requires the use of a Temperature Monitoring Device (TMD) such as an electronic Digital Data Logger (DDL) to ensure that the temperature during the storage and handling of the COVID-19 vaccines is maintained properly and safely.

Key Features of a Temperature Data Logger

A key feature when using an electronic data logger is the ability to accurately determine the temperature of the vaccine. Unlike a simple min/max recording thermometer, a DDL can provide information on temperature excursions – how long the vaccine has been outside of the recommended temperature range. These devices typically allow recorded data to be downloaded to a computer or sent to a web-based cloud storage service to maintain historical records for up to 3 years – the CDC recommended archival period. They also allow the user to specify how often a measurement is recorded, typically at least every 30 minutes or faster. Rather than simply recording temperature data, more advanced DDL’s can provide alarms, either local visual or audible alarms, or via email, SMS, or voice to provide immediate notification of temperature excursions or loss of power. The devices normally use some type of probe that is placed within the refrigerator or freezer compartment. To accurately reflect the actual temperature of the vaccine, the CDC recommends the use of a thermal buffer – glycol bottle, glass beads, or Teflon block – on the probe to dampen temperature fluctuations due to door openings, etc.

While the condensed CDC storage and handling guides do not address calibration, the CDC Storage and Handling Toolkit document, recently updated to include the COVID-19 vaccines, requires that the DDL used for temperature monitoring be calibrated with the National Institute of Standards and Technology (NIST) traceability. This is to ensure that the temperature recorded by the device is accurate to provide the best protection of the efficacy of the vaccines.

Furthermore, the CDC has published additional guidelines for the Moderna, Johnson & Johnson, and Pfizer vaccines. In the case of the Moderna vaccine and the Johnson & Johnson vaccine, it is preferred that the DDL provide a daily minimum and maximum temperature either on the display of the device or in the software. If this is not available, it is recommended that the recorded daily data be inspected to determine the minimum and maximum temperature.

The recommendations for the Pfizer vaccine are similar with the exception that the DDL be able to measure dry ice temperature -80° to -60°C for long-term storage. For both of these, they can be stored in a refrigerator between +2°C and +8°C for shorter periods of time prior to dispensing.

Vaccine Temperature Monitoring Solutions

So which digital data loggers available on the market are suitable to monitor the COVID-19 vaccines? CAS Dataloggers has provided leading solutions for vaccine storage in freezers and refrigerators for many years. With the approval and distribution of the COVID-19 vaccines in the US, interest, and sales of our vaccine storage monitoring data logger kits have increased dramatically. For small scale vaccine storage, there are two key kits:

T&D TR-75wb Kit for the Pfizer Vaccine storage (down to -199 Deg C)

T&D TR-71wb Kit for the Moderna and Johnson & Johnson Vaccine storage (down to -40 Deg C)

Each kit can monitor the temperature of two storage environments – with two temperature probes in each kit. Each kit comes ready to deploy and meets the CDC requirements for monitoring the storage temperature of the COVID-19 vaccines, including a NIST Traceable Calibration Certificate. Please be aware that local authorities may have additional requirements for calibration, for example, ISO 17025 traceability, so it’s important to check with your local governing body.

On top of solutions to monitor Covid-19 vaccines, we can also help you with any temperature monitoring solution from the smallest refrigerator to large-scale freezer farms or even transportation monitoring. Give us a call at 800-956-4437 or request more information.

The post Demand for Temperature Data Loggers to Monitor COVID-19 Vaccines appeared first on CAS Dataloggers.

While this post is tailored for Life Science applications (primarily Medical/Pharmaceutical spaces), it applies to most applications where product or material is stored in refrigerators or freezers. Temperature is recognized as the most widely measured physical parameter, and with good reason. The temperature has some effect on almost everything. In the Life Sciences area, the effects of temperature can make the difference in the efficacy of vaccines and the life or death of cells, embryos, or tissues. Ensuring that the stored materials do not get too warm or too cold is vital.

Here are some best practices to guide you through the setup and use of a temperature monitoring system:

Initial Setup & Configuration

Choose a sample rate that reflects the potential for your refrigerator/freezer to change. A faster sample rate equals more data over time, but that does not necessarily mean better data. The other consideration for the sample rate is the sensitivity of your material to temperature. If you have a relatively wide range of acceptable storage temperatures, you can accept a slower sample rate. A high sensitivity typically means a faster sample rate. In most cases, a 15 or 30-minute sampling interval is appropriate.

The alarm thresholds should be set so that you have enough time to react to the condition to save the material in the event of an excursion. If your ability to react to the alarm is measured in minutes rather than hours, your alarm settings can be closer to the limits. If the time it takes you to react is some number of hours, you may want the alarm settings to be further from the hard limits. It is also important to have an action plan in the event of an alarm so that you can implement that plan before the material is damaged.

Temperature Probe Placement

The position of the probe in the storage cavity is important, as it measures the temperature at a single point in space. That point should be where it best reflects the temperatures of the material in the refrigerator or freezer. If the refrigerator cools by forced air, having the probe in the airflow will yield more fluctuations than if it is in a still area of the refrigerator.

A thermal buffer should also be considered if the door to the refrigerator or freezer is opened at any frequency. When the door to a refrigerator is opened, cold air rushes out of the bottom of the opening, and warm air enters from the top. This creates a rapid change in air temperature in the cavity. However, the thermal mass of the material you are storing does not respond as quickly.

A thermal buffer surrounds the probe sensing tip with material that will dampen the temperature swings that the probe tip experiences. This more closely mimics most materials you store as their temperature does not change as rapidly as the air surrounding them. Thermal buffers can be solid nylon cylinders, glycol in a bottle, sand, or glass beads. You should also understand how the thermal buffer in concert with the sample rate affects your measurements. If the thermal time constant of the buffer is 10 minutes, a sample rate any faster than 10 minutes will essentially be useless.

Test the Alarms

You should test the function of the alarms before you rely on them. You need to ensure that the e-mail addresses and phone numbers for text messages or voice calls are actually received. Catching a mistyped character during configuration can prevent a loss in the future.

Review the Operation of Your System

In the early stages of using a temperature monitoring system, the data should be reviewed more frequently than in a system that has been in place for many years. You need to determine that the system is operating and functioning as you require. This means data is getting recorded as desired (sample rate). The data being recorded is meaningful and accurately represents what the stored material is experiencing. Do you see fluctuations in the measured temperature or is the reading unchanged no matter what is happening with the door to the refrigerator?

Create and follow a periodic review of the system and its functions. This is not a “set it and forget it” operation. Changes will happen that affect how the system is operating. Personnel changes require editing of the alarm contact lists. If the refrigerator or freezer is actively used, damage could occur to the probe wiring or the placement. By checking the data periodically, you can verify continued proper measurement and recording.

Calibration

You may be required to calibrate your temperature monitoring system. This process essentially means comparing the measurement of your probe and data logger against a known standard, frequently traceable to NIST standards or other national standards bodies. This ensures that the data is accurate.

By following these practices with your temperature monitoring system, you will gain the greatest benefits provided by an automated system and achieve the ultimate goal of meaningful data and protection against loss.

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