FloBoss 103/104 Instruction Manual
4-8
Input/Output
Revised August-2017
Figure 4-8. Pulse Input Wiring
4.8 RTD Input
The temperature is input through the Resistance Temperature Detector
(RTD) probe and circuitry. The RTD temperature probe mounts directly
to the piping using a thermowell, outside the FloBoss enclosure. The
RTD probe is then wired to the FloBoss RTD connections. The RTD
wires should be protected either by a metal sheath or by conduit
connected to a liquid-tight field conduit wiring fitting on the enclosure.
The RTD signal is monitored by a 16-bit A/D converter and then read
by the microprocessor.
4.8.1 Wiring the RTD Input
The RTD wires connect to the three screw terminals designated “RTD”
on the Termination board.
The FB100 provides terminations for a three-wire or two-wire 100-ohm
platinum RTD with a DIN 43760 curve. The RTD has an alpha equal to
0.00385
Ω
/
Ω
.
Wiring between the RTD probe and the FB100 should be shielded wire,
with the shield grounded only at one end to prevent ground loops.
Ground loops can cause RTD input signal errors.
shows the connections at the RTD terminals for the various
RTD probes
Table 4-1. RTD Signal Routing
Terminal
Designation
3-Wire RTD
2-Wire RTD
+
Signal positive input
RTD +
RTD +
+
Signal positive input
RTD +
Jumper to RTD +
RET
Return reference
RTD RET
RTD RET
