Instruction manual

Output Wiring
continued
RFT9739 Field-Mount Transmitter Instruction Manual 33
Output Wiring Startup TroubleshootingBefore You Begin Getting Started Mounting
Power-Supply and
Sensor Wiring
Configuration for open
collector mode
The RFT9739 provides current to the frequency/pulse output circuit. In
applications where this current must be permanently suspended, and for
receiving devices that require input voltage higher than approximately
10 volts, the frequency/pulse output circuit can be used in open collector
mode.
To configure the output for open collector mode, a resistor must be
clipped as described below.
This procedure will permanently alter the
transmitter and cannot be reversed.
• Clip resistor R14 (R1 on models with enhanced EMI immunity) and add
an external DC power supply and a pull-up resistor. See
Figure 5-8
.
• The pull-up resistor must be of sufficient value to limit loop current to
less than 0.1 ampere, depending on the total loop resistance at the
transmitter.
• Resistor R14 (R1) is located on the RFT9739 output board, behind the
output terminal blocks, as illustrated in
Figure 5-9
. To access resistor
R14 (R1), unplug the output terminal blocks from the transmitter.
CAUTION
Clipping resistor R14 or R1 will eliminate the internal
voltage source from the transmitter.
After clipping resistor R14 or R1, an external power supply
is required to use the transmitter’s frequency/pulse output.
Before permanently altering any equipment, contact the
Micro Motion Customer Service:
• In the U.S.A., phone [phone]
• Outside the U.S.A., phone [phone]
• In Europe, phone [phone]
• In Asia, phone [phone]