30
RFT9739 Rack-Mount Transmitter Instruction Manual
Output Wiring
continued
5.4
Frequency outputs
The RFT9739 frequency outputs include a frequency/pulse output, a
dual-channel phase-shifted frequency output for custody transfer
applications, and an optocoupler output.
• The frequency output loops are isolated and floating from other circuits
except the control output and external-zero input circuits. Ensure that
frequency output loops are grounded properly, either at the transmitter
end, or at the external device.
• The frequency output circuit uses a 2.2 kohm resistor tied to a 15-volt
source that limits the current to 7 mA. The output circuit is rated to
30 VDC, with 0.1 ampere maximum sinking capability, when used in
open collector mode. Open collector mode is described on page 33.
• The output is a n15 V or +30 V square wave, unloaded. See
"Setting voltage level for VDE output requirements," page 37.
• Output impedance is 2.2 kohm.
• For use with receivers other than Micro Motion peripheral devices,
check the instruction manual for the receiver to make sure its input-
voltage and electrical-current ratings match the RFT9739 ratings.
Frequency/pulse output
The frequency/pulse output represents the flow rate, independent of the
primary and secondary mA outputs. The frequency/pulse output can be
used with all Micro Motion peripheral devices except the DMS Density
Monitoring System and the PI 4-20 Process Indicator, which do not have
frequency inputs.
The RFT9739 frequency/pulse output can be configured to provide any
one of the following:
• Mass flow rate
• Volume flow rate
• Mass flow total
• Volume flow total
Mass flow total and volume flow total are not available with some
RFT9739 transmitters shipped prior to 1998.
Use RFT9739 terminals CN2-D24 and CN2-D26 for the frequency/pulse
output. Terminal D26 serves as a common return for the frequency/pulse
output, dual-channel frequency output, control output, and remote zero
input. See Figure 5-5, page 31.
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