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3-14 Section 3: Installation
February 3, 2000 70055MP Revision D
LTC-MAP Power
OEM potentiometers that are not powered require power from the LTC-
MAP’s 24 VDC Sensor Power Supply. To use the LTC-MAP supply, you
must:
• Select a Voltage Drop Resistor (R
d
).
• Connect the Power Supply wires to the OEM Potentiometer.
• Connect the wires at the Monitor Circuit board.
In order to use this power, you must first calculate the value of the required
voltage drop resistor (R
d
). The voltage drop resistor limits the current and
voltage across the potentiometer (see Figure 3-8).
Figure 3-8: Typical OEM Potentiometer Powered by LTC-MAP
To calculate R
d
:
1. Determine the value and number of resistors in the potentiometer.
NOTE: LTC-MAP can accommodate any value or number of tap
position resistors.
2. Calculate the String Resistance (Rs) where:
Rs = (Resistor Value) x (Number of Resistors).