Omega Vehicle Security OMP-MODL Thermocouple Application Notes, Signal Connection all Ranges

VDC- Lo

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VDC-

Medium

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3... INTERFACE MODULES

Thermocouple Application Notes:

Cold Junction Compensation (CJC): For thermocouple measurements, the temperature of the terminal strip connections is required in the voltage to temperature conversion equation used by the OMP-MODL. This temperature is measured by the CJC sensor located in the MLAD-1 module. Any differential temperature from the metal terminal strip connections to the CJC sensor on the MLAD-1 circuit board will result in direct measurement errors.

The MLAD-1 is thermally designed to provide good CJC sensor vs terminal strip temperature tracking however, to minimize this potential error, avoid installations or effects that will induce extreme temperature differential. The most accurate readings will be achieved when the OMP-MODL has been allowed to temperature stabilize. In rapidly changing temperature environments, additional accuracy can be achieved if the OMP-MODL is housed within another enclosure providing better temperature equalization throughout the system.

DIFFERENTIAL POTENTIAL: to minimize current loop induced errors, use isolated type thermocouples (ie thermocouples that are not in electrical contact with a conductive surface to which they are attached) or insure that all thermocouple junctions are at ground potential. Insure that input voltages do not exceed 3.0V above or below circuit ground (maximum common mode voltage).

MLIM-1; DC VOLTAGE APPLICATION

The MLIM-1 can support three different major ranges (and a multitude of sub- ranges) of analog DC voltage input depending on the channel’s hardware Configuration Switch setting (See Table 3... -4). To utilize an MLIM-1 channel as a DC Voltage input, set that channel’s Configuration Switch per the Table for the desired input signal range.

As shown in Figure 3... -12, when DC-MED or DC-HI are selected with the hardware Configuration Switches, front-end divider circuitry is enabled. This circuitry attenuates the input signal to a range that can be handled by the MLIM-1 instrumentation amplifier section.

TIP: For best accuracy and absolute resolution, utilize the lowest range possible that will cover the input signal’s dynamic range without over-ranging.

Signal Connection (all Ranges):

Interface Module channels configured as VDC inputs provide three terminal strip connections per input; Positive lead, Negative lead, and Shield.

Connect the VDC signal positive and negative leads to the correct pair of terminals on the module terminal strip (Figure 3... -15). Refer to Chapter 7 for steps to generate a Terminal Strip Wiring printout for use in making field wiring connections.

Observe polarity or the output signal will be reversed.

USING THE OMP-MODL 3-25