Omega Vehicle Security OMP-MODL MLIM-4 RTD Input Application, MLIM-4 Thermistor Input Application

RTD Input

Thermistor

Input

Resistance

Input

3... INTERFACE MODULES

MLIM-4; RTD INPUT APPLICATION

The RTD function of the MLIM-4 allows for the input of Platinum RTD’s with any of the following characteristics:

♦100 or 1000 ohm @ 0’ C

♦European (0.0385) or American (0.0392) alpha coefficient curve

♦2, 3, or 4-wire configuration

The actual temperature is calculated from the resistance and can be output in either degrees C or F. Two input temperature ranges are provided for maximizing span and ultimate resolution of the readings. The RTD element resistance is measured using a constant current ratiometric technique which provides excellent accuracy and stability over time and temperature.

Refer to the Excitation Current Table for current levels utilized in the excitation of the RTD elements.

MLIM-4; THERMISTOR INPUT APPLICATION

The Thermistor function of the MLIM-4 allows for the input of 10,000 ohm @ 25C NTC thermistors conforming to the Fenwall Curve 16 or equivalent RT curve.

The actual temperature is calculated from the resistance and can be output in either degrees C or F. Four input temperature ranges are provided for maximizing span and ultimate resolution of the readings. The Thermistor element resistance is measured using a constant current ratiometric technique which provides excellent stability over time and temperature. Due to the high resistance vs temperature ratio, only 2-wire configuration is provided (and required).

Refer to the Excitation Current Table for current levels utilized in the excitation of the Thermistor element under test.

MLIM-4; RESISTANCE INPUT APPLICATION

The Resistance function of the MLIM-4 can measure resistances ranging from 200 ohm to 400,000 ohm full scale. 2, 3, or 4-wire configurations can be used depending on absolute accuracy requirements.

Twelve input resistance ranges are provided for maximizing span and ultimate resolution of the readings. The resistance is measured using a constant current ratiometric technique which provides excellent stability over time and temperature.

Refer to the Excitation Current Table for current levels utilized in the excitation of the resistance elements being measured.

MLIM-4; INPUT SIGNAL CONNECTION METHODS:

For all three signal types, RTD, thermistor, and resistance, a ratiometric resistance measurement technique is used. In the case of the RTD and thermistor measurements, a software conversion is then used to convert this resistance into temperature.

In measuring the resistance of a distant element with a conventional 2-wire connection configuration, the resistance of the lead wires running from the module terminal strip to the actual sensing element itself will add resistance and corresponding error. The magnitude of these errors depends on the resistance of the lead wires which is a function of wire gauge, temperature, and any connection resistance. If the resistance is small relative to the resistance being measured, this

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