TCSMA Conductivity System
Part 4 – Transmitter Electrical Installation
O & M Manual
15
REV G, 7/2009
Figure 4-1 Loop-Power Connection
4.3 Load
Drive
The two-wire instrument can operate on a power supply
voltage of between 16 and 35 VDC. The available load drive
capability can be calculated by applying the formula V/I=R,
where V=load drive voltage, I=maximum loop current (in
Amperes), and R=maximum resistance load (in Ohms).
To find the load drive voltage of the two-wire TCSMA,
subtract 16 VDC from the actual power supply voltage being
used (the 16 VDC represents insertion loss). For example, if
a 24 VDC power supply is being used, the load drive voltage
is 8 VDC.
The maximum loop current of the two-wire TCSMA is always
20.00 mA, or .02 A. Therefore,
TRANSMITTER
POWER SUPPLY
24 VDC
LOAD
(+)
(-)
(+)
(-)
(+) (-)
(Power Supply Voltage - 16)
.02
=
R
MAX
