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What is the voltage used on a universal input (UI) on a MNL-20Rx controller?

Issue

What is the voltage used on a universal input (UI) on a MNL-20Rx controller?

Environment

MNL-20Rx Controller

Cause

Information on the input types the MNL-20Rx Controller accepted.

Resolution

UI circuits output (5.0 Vdc) and are designed to process the following input types: 1K Balco RTD, 1K Platinum RTD, 10K thermistor with 11K shunt resistor, Voltage 0 to 5 VDC, Current 0 to 20 mA with external shunt, 0-1K resistance range, 0-10K resistance range, and a digital contact closure.

For resistive type inputs, the microprocessor controls an internal multiplexer that switches and pulses the various current sources to the various UIs during the analog to digital (A/D) process. The circuit does not apply a constant current to the sensor on a continuous basis.

A voltage value will be read across the resistive sensor.  However this reading is not accurate due to the pulse methodology. The current pulsed to the sensors depends upon the range. The 10K thermistor with 11K shunt resistor is pulsed with 0.45 mA and the 1K RTD sensors (e.g. Balco and Platinum) are pulsed with the 3.1 mA current source.

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