Omega Vehicle Security OMP-MODL manual Wire Terminal Strip Connections, Wire Compensation Theory

3... INTERFACE MODULES

2-Wire Terminal Strip Connections:

The MLIM-4 module is provided with a 12 position terminal strip. Each MLIM-4 input channel utilizes 3 of the 12 terminals (1-2-3, 4-5- 6, 7-8-9, 10-11-12). Connect the input signal to the first two of the three input terminals (1-2, 4-5, 7-8, 10-11) on the terminal strip. A wire jumper must then be installed from the second to the third terminal (2-3, 5-6, 8-9, 11-12).

Refer to Chapter 6 for steps to generate a Terminal Strip Wiring printout after construction of a Program Net for use in making field wiring connections.

		A			B			C		D
	1	2	3	4	5	6	7	8	9	10 11 12
RTD Element
					Jumper
Cable Shield	Connect Shield to an Earth Ground
										ML125
Figure 3... -28; 2-Wire Configuration

For long lead wire runs and in applications in electrically noisy environments, it is recommended that twisted pair and/or shielded wire be used. If shielded wire is used, the shield at the OMP-MODL end should be connected to an external earth ground (Figure 3... -

28)or if available, a grounded Shield connection provided on another type installed interface module (such as the MLIM-1).

3-Wire Config

3-Wire Configuration

The 3-wire configuration is used in applications where the lead wire effects calculated as above will have a significant error inducing effect on the resistance measurement. The 3-wire configuration requires two input channels (A and B or C and D) to implement. From within the HyperNet Window, double-clicking Channel A or C icons displays a dialog and allows for selection of 2, 3, or 4-wire connection. When 3 -wire is selected, a second corresponding icon (Channel B or D) is removed as this second channel is required for the 3 -wire measurement.

3-Wire Compensation Theory:

With a 3-wire configuration, the resistance of one of the lead wires is measured, doubled and then subtracted out of the measured total element plus lead wire circuit resistance. The 3-wire configuration, as the name implies, requires the use of three discrete wires from the module terminal strip to the element. Two of the leads connect to one common end of the element and the other lead connects to the other end of the element. The 3-wire configuration provides

3-42 USING THE OMP-MODL