Output Wiring
continued
RFT9739 Rack-Mount Transmitter Instruction Manual
41
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Control output in open
collector mode
The RFT9739 provides current to the control 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 control output circuit can be used in open collector mode.
If the frequency/pulse output is configured for constant current (see
"Configuration for open collector mode," page 33), the control output is
rendered inoperable. To reconfigure the control output to function
properly, independent of this frequency/pulse output configuration, the
control output circuit can be configured for open collector mode.
To configure the control 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 R4 and add an external DC power supply and a pull-up
resistor. See Figure 5-17, page 42.
• 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.
• To prevent damage to the optocoupler and dual-channel frequency
output circuits, the external voltage must not exceed 15 V.
• Resistor R4 is located on the inside of the RFT9739 back panel.
To access resistor R4, refer to Figure 5-18, page 42, and follow these
steps:
1. Remove the bottom cover of the transmitter housing.
2. Remove the back panel, and carefully pull it loose from the power
board and the control board.
3. Locate and clip resistor R4 on the inside of the RFT9739 back panel.
4. Reinstall the bottom cover.
5. Reinstall the back panel, carefully aligning the connector pins with the
connectors on the power board and the control board.
CAUTION
Clipping resistor R4 will eliminate the internal voltage
source from the transmitter.
After clipping resistor R4 an external power supply is
required to use the transmitter’s control output.
Before permanently altering any equipment, contact the
Micro Motion Customer Service:
• In the U.S.A., phone 1-800-522-6277, 24 hours
• Outside the U.S.A., phone 303-530-8400, 24 hours
• In Europe, phone +31 (0) 318 549 443
• In Asia, phone 65-770-8155
Содержание Fisher Rosemount RFT9739
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