White Paper: How to Prevent Temperature Measurement Errors
Nearly two-thirds of all temperature measurement in the US makes use of the thermocouple in some form. Likewise, most industrial applications remotely sense temperature using thermocouples, and optionally transmit the thermocouple signal some distance using industrial transmitters for the purpose of monitoring and controlling a process. An industrial transmitter is commonly used to amplify, isolate, and convert the low-level thermocouple signal to some other signal suitable for monitoring or retransmission. Unfortunately, the interface between these sensors and their mating instruments is widely misunderstood and this leads to system error. With a little understanding of thermocouples and how they work, these errors could be avoided. This paper will focus on the connectivity aspects of thermocouples and temperature transmitters, but can be extended to include any thermocouple instruments.
File:
How_to_prevent_temperature_measurement_errors_when_installing_thermocouple_sensors_and_transmitters_926A.pdf
White Paper: Temperature Measurement Using Thermocouples 8500-911 (part 1)
Abstract: You are probably somewhat familiar with the thermocouple, but you must understand that choosing the type (J, K, T, etc.) is not as simple as just picking a compatible temperature span. You must give consideration to the sensor materials, the ambient temperature range, the sensor's sensitivity, and its reaction with the measurement environment. You must also be aware of the inherent limitations of the thermocouple and potential error sources. This white paper will help you to make an informed selection between sensor types and avoid potential problems in your application. Part 1 of 3
File:
Thermocouple_Temperature_Measurement_911A.pdf
White Paper: Temperature Measurement Using RTDs 8500-917 (part 2)
Abstract: A RTD or Resistance Temperature Detector is a passive circuit element whose resistance increases with increasing temperature in a predictable manner. In choosing one you must consider a RTDs temperature coefficient of resistance (TCR), its relative sensitivity, its accuracy and repeatability, interchangeability, stability and drift characteristics, its insulation resistance, its response time, plus its packaging and the thermal transfer mechanism between the sensed material and the sensor element. You must also consider the negative effects of corrosion and contamination, shock and vibration, self-heating, meter loading, and in some cases, even thermoelectric effects. (part 1, 8500-911; part 3, 8500-918)
File:
RTD_Temperature_Measurement_917A.pdf
White Paper: Thermocouple and RTD Temperature Sensor Selection 8500-918 (part 3)
Abstract: This white paper will summarize and compare some common aspects of both sensors to help you choose between the two in your quest to find the best sensor for your particular industrial application. Part 3 relies heavily on information provided in parts 1 and 2 and you should review parts 1, 8500-911 and 2, 8500-917 before reading this material.
File:
Comparison_of_Thermocouple_and_RTD_Temperature_Sensors_918A.pdf
Whitepaper: Introduction to the Two-wire Transmitter & the 4-20mA Current Loop
Abstract: In many control loops, we use two-wire transmitters to convert various process signals representing flow, speed, position, level, temperature, pressure, strain, pH, etc., to 4-20mA DC for the purpose of transmitting the signal over some distance with little or no loss of signal. This paper reviews the operation and advantages of the 4-20mA transmission standard and the use of loop-powered transmitters.
File:
Acromag_Intro_TwoWire_Transmitters_4_20mA_Current_Loop_904A.pdf
