UM344-2 INSTALLATION
September 1995
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4.3.4.1 Point-To-Point Network
Figure 4-4 defines an analog mode Transmitter's operating region for the allowable ranges of supply
voltage and network resistance. Perform the following simple calculations to ensure that the power supply
output voltage permits the Transmitter to remain within the indicated operating range.
1. Calculate the minimum power supply output voltage.
The minimum network power supply voltage requirement is a function of Network Resistance and full
scale current (22.5 mA), and is calculated by the following formula:
Minimum Power Supply Output Voltage = 12 volts + (0.0225 x Network Resistance in ohms)
Power supply output voltage must be greater than the calculated value. The minimum voltage across
the input terminals of a Transmitter is 12 volts.
2. Calculate the maximum power supply output voltage.
The maximum network power supply voltage is a function of Network Resistance and zero scale
current (3.85 mA), and is calculated by the following formula:
Maximum Power Supply Output Voltage = 42 volts + (0.00385 x Network Resistance in ohms)
Power supply output voltage must be less than the calculated value. The maximum voltage across the
input terminals of a Transmitter should never exceed 42 volts.
4.3.4.2 Multi-Drop Network
Perform the following simple calculations to ensure that the power supply output voltage permits the
Transmitter to remain within its operating range.
1. Calculate the minimum power supply output voltage.
Minimum network power supply voltage is a function of Network Resistance and the total current
draw of all transmitters in the Network, and is calculated by the following formula:
Minimum Supply Output Voltage = 12 volts + [(0.004 x number of transmitters on Network) x (Network Resistance)]
Power supply output voltage must be greater than the calculated value. The minimum voltage across
the input terminals of a Transmitter is 12 volts.
2. Calculate the maximum power supply output voltage.
Maximum network power supply voltage is a function of Network Resistance and total current draw
of all the transmitters in the Network, and is calculated by the following formula:
Maximum Supply Output Voltage = 42 volts + [(0.004 x number of transmitters on Network) x (Network Resistance)]