Continuous & Process Monitoring FAQs

The best way to use a glass thermometer as an accurate measurement instrument is to:

1) only do so in a well-stirred liquid medium

2) only use it at its rated immersion depth

3) do not use it at temperatures too far from ambient.

Mercury and glass thermometers can be accurate if they are used in the situations and environments they were designed for. Many glass thermometers are rated as full immersion; this means that to achieve their rated accurately they must be fully immersed in the environment they are measuring, frequently this is air. These types of thermometers are appropriate for environmental measurements, not for use in liquid mediums.

There are glass thermometers that are calibrated and designed for measurements in liquid. However, it is even more critical that immersion depth be observed with these units. As suggested above all temperature measuring devices have a rated immersion depth, at which there will be no measurable stem effect from heat being conducted to or from the ambient environment along the stem to or from the tip. Failure to adhere to the immersion depth requirement will introduce significant inaccuracies into the measurement.

Finally, the further from ambient that the target temperature is, the more errors can creep into the measurement due to procedural or equipment related issues.

Assuming that proper care is taken in the preparation of these processes, it is possible to verify loggers in these mediums, but it can be difficult to obtain the stability and uniformity required using “common materials”.

First it must be recognized that water boils at 100°C and freezes at 0°C only at sea level. Second, the water used must be ultra pure. Impurities will change both the boiling point and freezing point observed. Finally, the higher in altitude (above sea level) that the verification is performed, the lower the boiling point of water. All of this suggests that a well calibrated reference standard should be used to verify the actual target temperature even in these “known” environments.

The vessel used should be one that is more stable and uniform than a pot on a hotplate. A liquid medium that is not well stirred or isolated from the outside environment will be neither stable nor uniform. Furthermore, the bottom, sides and top can be at significantly different temperatures than the middle.

Physically, it is possible to make the tip 0.5 inches (13mm), less than that creates problems with welding the probe tube, and also, the installation of the sensor into the probe tip, especially the RTD.

Of greater concern is the thermal affect caused by the base on the temperature observed by the sensor. In the Micropack MPIII, tests found in certain environments that the base acted to influence the sensor’s temperature readings. Obviously, this depends on the environment and how the logger is fixed in the product/process, but there was an observable impact in many situations.

Obviously, the MPIII is much smaller and less of an impact would be expected, but we expect an observable impact in certain situations where the probe tip is less than one inch in length.

Yes, all of our DataTrace equipment (Loggers and PC Interfaces) carry the CE mark. The specific requirements relate to the following EC Standards or Norms for Electromagnetic Compatibility: EN 55022 and EN 50082-2.

The freezing issue could be caused by using an older version of the USB driver installed on your computer. To verify the version of the currently installed driver, please follow the steps below:

1. Click on Start button, then select Control Panel.
2. Click on System properties
3. Select Device Manager
4. Double-click to expand Universal Serial Bus controllers section at the bottom of the list.
5. With the USB MPIII Interface plugged into the computer, there should appear a “DataTrace MPIII USB PCIF” item in the USB controllers list.
6. Double-click on the “DataTrace MPIII USB PCIF” item to launch its Properties window.
7. Click on the Drivers tab.
8. If you have any version that is older than 2.0.0, then please see the attached instructions on how to upgrade to the latest version.

There are several causes of the errors on launch of DT Pro.  See our DT Pro 1.3 Troubleshooting Guide to find the solution that is right for you.

The short answer is that the humidity logger’s sensor can not usually be cleaned. The sensor’s manufacturer does not recommend attempting to clean the sensor, either chemically or by any form of scrubbing as it is likely to cause damage. The humidity sensor has a moisture-sensitive polymer on a ceramic substrate. These components are extremely thin and are sensitive to abrasion. Damage to, or removal of the polymer will destroy the sensor. At best trying to clean the sensor will worsen the affects of the contamination.

The best approach if you believe the logger’s sensor has become contaminated is to perform a humidity verification. If the calibration is determined to be out of specification, either do a field calibration on the existing sensor replace the logger’s sensor with a new sensor, or return the humidity logger to the factory for a refurbishment.

Cleaning of the pressure sensor is possible if extreme care is employed. Under no circumstances should swabs, picks, or any other instrument or tool be used in contact with the diaphragm. The diaphragm should never be touched; even the slightest pressure will adversely impact the device and its accuracy.

To start the cleaning process, carefully remove the protective cap by unscrewing it from the probe base.

For any coating or process residue adhering to the diaphragm, it is best to soak it off before it dries.

For cases where the coating or process residue adhering to the diaphragm has already dried, let the Logger soak in warm water with a mild detergent until the contamination softens. Then rinse it off with a LOW PRESSURE water stream.

In severe cases of contamination, a solvent may be necessary. Use a solvent for the specific contamination material. Since the diaphragm is stainless steel, most solvents will not affect it. If you have a question regarding a specific solvent, contact the factory.

It is critically important that the diaphragm is not touched, scrubbed, picked at, pushed on or probed. This can cause permanent damage.

Battery life can be extremely difficult to estimate and is not a precise value. Batteries have a very wide variation in life cycles from one battery to another of the same type. In our experience battery life in general is very much affected by three application-driven situations:

1) How frequently the logger is used
2) The temperature extremes and the duration of those extremes to which the logger is exposed, and
3) The Sample Interval defined.

The MPIII Logger uses a considerably small battery. Based on initial process testing and our normal on-going testing, we expect the battery life for MPIII loggers to be approximately 2 to 3 months with similar caveats as above. However, the MPIII loggers have a battery life indicator that displays an estimated remaining battery life when the logger is tested or programmed.

The pressure logger and humidity logger will consume, normally, twice as much power as the temperature-only logger, while the humidity logger is between these extremes.

MPRF logger battery life is also estimated automatically in DT Pro and shows a percentage indicator in all relevant screens. Please make sure to indicate what battery type you are using when changing batteries within DT Pro.

The pressure logger’s pressure sensor responds to changes in pressure almost instantly (< 1 second). The observed pressure will be accurate providing that the pressure logger is in an isothermal (stable temperature) environment. If the temperature is changing, the observed pressure can be in error by as much as two (2) PSIA.

Mesa’s Medical Division is qualified to the ISO 13485/13488 standard and is registered as a Medical Device manufacturer with FDA, under registration number 1720309 and with Canada (CMDR). Appropriate portions of this rigorous quality control system are also utilized by the DataTrace Division.

The DataTrace Compliance and Certification (form 339) certifies not only the Software Validation but also the FDA-based quality system for DataTrace and the NIST-traceable calibration system. Unlike an ISO certificate, it gives more detail about our quality system. Our Quality Assurance Manual is designed to substantially comply with all the criteria of ISO 9001. This document is revised to keep it current with new products, changing requirements, and technologies.
The DataTrace Calibration Laboratory is also ISO17025 Certified for all procedures. The relevant certificates can be found at our website here: DataTrace Certifications.

The logger does not have a clock, but uses a timing circuit, based on a highly accurate oscillator (approximately 30ppm). As with all oscillators, high temperature affects them. However, in the case of the oscillator used in your logger, the actual impact is not significant. For example, in the worst case where a logger was operating at 150°C for 24 hours, the timing would be off less than 30 seconds.

Timekeeping accuracy is evaluated inherently as part of the calibration process for each logger.

Initially, during the calibration procedure, the logger is programmed on the computer which is used to operate the calibration bath and log the reference temperatures. Following programming, the logger is immersed in the bath and the computer commands the bath to go to a certain temperature. When the bath software detects that the bath temperature is stable enough, measurements are taken with the reference thermometers. After the measurements are recorded, the bath is commanded to change to the next calibration temperature.

This procedure is repeated every 5°C throughout the logger’s temperature measurement range. After the calibration data is acquired from the reference thermometers during the calibration process, the logger is removed from the bath, cleaned and read.

The data that the computer acquired during calibration includes the temperature at each stable point, and the exact time these data points were taken. This reference data is then compared to the readings from the logger, at each point in time. If the logger timekeeping were not accurate, it could not pass the calibration or calibration accuracy verification. Even if the logger calculated the proper temperature, if the point in time were off by even a few seconds during this 7 to 9 hour process, the wrong temperature would be compared to the reference temperature and the logger would fail.

A thermocouple is based on the principle that an electromagnetic force (emf) is generated when heat is applied to the junction of two dissimilar metals (sensing junction). At the other end of the wires, usually as part of the input instrument, is another junction, called the reference junction. The temperature is inferred based on the emf difference between the sensing junction and the reference junction, which is at a known temperature.

Advantages of thermocouples:

Low cost, rugged, small size/fast response, wide temperature range, and reasonably accurate.
Disadvantages of thermocouples:

Weak emf signal, calibration affected by temperature gradients and material contaminants, affected by electrical interference, calibration drifts following calibration.
An RTD is based on the principle that the electrical resistance of a metal increases as its temperature increases. The RTD sensing element consists of pure metal (frequently platinum) and shows a small positive, linear change in resistance per degree of temperature change.

Advantages of RTDs:

High repeatability and stability, high accuracy over wide range, rapid response, and small sensor size.
Disadvantages of RTDs:

High cost, fragile, susceptible to emf interference and self-heating, not suitable for extremely high temperatures.
A thermistor is a thermally active resistor composed of metal oxides normally encapsulated in epoxy or glass. A typical thermistor shows a large negative, nonlinear change in resistance per degree of temperature change. A thermistor’s resistance drops dramatically and non-linearly with temperature.

Advantages of thermistors:

Inexpensive, long-term stability, high accuracy, temperature coefficient is greater than metals, rugged, small size/fast response, high sensitivity, senses at a single point, and requires simple circuitry.
Disadvantages of thermistors:

Temperature resistance curve is non-linear, relatively narrow range, and not suitable for high temperatures.

The environmental temperature recorded by a temperature-only logger and the temperature value recorded by a humidity logger can be significantly different, and is expected. The primary purpose of a temperature-only logger is to measure the environment next to the sensor; regardless of what that environment is (e.g., air, liquid, meat, etc.). The temperature sensor’s primary purpose in a humidity logger is not to measure the environment; it is to measure the temperature of the humidity sensor. This means the logger is “temperature compensated”. The compensation corrects the humidity reading for the actual temperature the humidity sensor is experiencing – the temperature of the humidity sensor.

This is why the temperature reported in a changing environment will be different between a humidity logger and a temperature-only logger. As the temperature in the environment stabilizes, the temperature readings will become closer, eventually becoming the same.

Again, keep in mind that the primary purpose of the humidity logger is to provide accurate humidity values and the primary goal of the temperature logger is to provide accurate temperature values. The methods of accomplishing these goals are not the same for both types of loggers, as indicated above.

The environmental temperature recorded by a temperature-only logger and the temperature value recorded by a pressure logger can be significantly different. This is expected. The primary purpose of a temperature-only logger is to measure the environment next to the sensor; regardless of what that environment is (e.g., air, liquid, meat, etc.) The temperature sensor’s primary purpose in a pressure logger is not to measure the environment; but to measure the temperature of the pressure sensor. This means these loggers are “temperature compensated.” The compensation corrects the pressure reading for the actual temperature the pressure sensor is experiencing – the temperature of the pressure sensor. The environmental temperature may not necessarily be the same.

This is why the temperature reported in a changing environment will be different between a pressure logger and a temperature-only logger. As the temperature in the environment stabilizes, the temperature readings will become closer, eventually becoming the same.

Again, keep in mind that the primary purpose of the pressure logger is to provide accurate pressure values and the primary goal of the temperature logger is to provide accurate temperature values. The methods of accomplishing these goals are not the same for both types of loggers, as indicated above.