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OM-USB-TEMP-AI User's Guide
Once the resistance value is calculated, the value is linearized in order to convert it to a temperature value. The
measurement is returned by software as a 32-bit floating point value in a voltage, resistance or temperature
format.
Data linearization
An on-board microcontroller automatically performs linearization on RTD and thermistor measurements.
RTD measurements are linearized using a Callendar-Van Dusen coefficients algorithm (you select DIN,
SAMA, or ITS-90).
Thermistor measurements are linearized using a Steinhart-Hart linearization algorithm (you supply the
coefficients from the sensor manufacturer's data sheet).
USB connector
The USB connector provides +5V power and communication. No external power supply is required.
LED
The LED indicates the communication status of the OM-USB-TEMP-AI. It uses up to 5 mA of current. The
table below defines the function of the OM-USB-TEMP-AI LED.
LED
Indication
Illumination
Steady green
The OM-USB-TEMP-AI is connected to a computer or external USB hub.
Pulsing green
Data is being transferred.
Upon connection, the LED should flash three times and then remain lit (indicates a successful
installation).
Power
The
terminal is isolated (500 VDC) from the USB +5V.
+5V
Caution!
The +5V terminal is an output terminal. Do not connect to an external power supply or you may
damage the OM-USB-TEMP-AI and possibly the computer.
LED Illumination
20
Functional Details
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