Can I Make Thermistor Measurements with the SCC-RTD01?Hardware: SCC>>Carriers>>SC-2345
Problem: I would like to make temperature measurements with a thermistor. Can I use the SCC-RTD01? Solution: Whether you can use the SCC-RTD01 to take temperature measurements with a thermistor depends on the resistance range of the thermistor. The maximum allowable voltage for the SCC-RTD01 is 400 mV when used with E Series DAQ devices. This is because E Series DAQ devices have a maximum input range of +/- 10 V, and the SCC-RTD01 applies a gain of 25, resulting in a maximum allowable voltage of 400 mV (10 V / 25). Also, the SCC-RTD01 module provides a 1 mA current excitation source. This excitation source results in a maximum resistance of 400 Ohms (400 mV / 1 mA). Because most thermistors have a resistance of a few thousand Ohms, you cannot measure them with the SCC-RTD01. As an alternative, you can use the SCC-CO20 to provide 0 to 20 mA of current to the thermistor. Then, you can use a SCC-AIXX module to read the voltage. This combination allows more flexibility in terms of current source and gain applied to the resulting voltage. However, keep in mind the range of current output and voltage input you are expecting for the SCC-CO20 and the SCC-AIXX respectively. Operating at very low ranges for either module could cause significant errors in the measurements. For example, if you try to use the SCC-CO20 module to supply 10 micro Amps, the resolution of the module is not high enough to ensure that the ratio of input voltage to output current stated in the manual is exactly correct. Likewise, if you are trying to read 0.01 Volts using a SCC-AI01 (+/-40 V), the resolution is not high enough to accurately measure this value and you would need to use something with a smaller range such as the SCC-AI05 (+/- 1 V), or the SCC-AI04 (+/- 100 mV). Related Links: Products & Services: SCC Product Manuals: SCC-CO20 Isolated Current Output Module User Guide Product Manuals: SCC-AI Series Isolated Analog Input Modules User Guide Attachments:
Report Date: 11/08/2002 Last Updated: 12/09/2005 Document ID: 2R7D7H0Q |
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