FCI ST100A Series, Installation, Operation And Maintenance Manual

Page: 103 / 170

ST100A Series Flow Meter TROUBLESHOOTING
Fluid Components International LLC 95
Troubleshooting the Flow Element
Check the Resistance of the Flow Element
Turn flow transmitter power OFF. Remove the TB1/TB2 connector plug from the sensor wiring pin socket (pull plug straight out).
Measure the resistance between the terminals of the pulled connector plug and compare with the values shown in
Table 28 below.
Table 28 – Flow Element Resistance Measurements (In Ohms) Taken From Remote/Integral Electronics
Term
Number
TB1/2-1
(Htr Exc)
TB1/2-2
(Htr Rtn)
TB1/2-3
(Act Exc)
TB1/2-4
(Act Sen)
TB1/2-5
(Gnd Sen)
TB1/2-6
(Gnd)
TB1/2-7
(Ref Exc)
TB1/2-8
(Ref Sen)
TB1/2-1
(Htr Exc)
N/A 115
3
∞ ∞ ∞ ∞ ∞ ∞
TB1/2-2
(Htr Rtn)
115
3
N/A ∞ ∞ ∞ ∞ ∞ ∞
TB1/2-3
(Act Exc)
∞ ∞ N/A 0
1
1080
2
1080
2
2160
2
2160
2
TB1/2-4
(Act Sen)
∞ ∞ 0
1
N/A 1080
2
1080
2
2160
2
2160
2
TB1/2-5
(Gnd Sen)
∞ ∞ 1080
2
1080
2
N/A 0
1
1080
2
1080
2
TB1/2-6
(Gnd)
∞ ∞ 1080
2
1080
2
0
1
N/A 1080
2
1080
2
TB1/2-7
(Ref Exc)
∞ ∞ 2160
2
2160
2
1080
2
1080
2
N/A 0
1
TB1/2-8
(Ref Sen)
∞ ∞ 2160
2
2160
2
1080
2
1080
2
0
1
N/A
Notes: 1. Theoretical zero-ohm table values are influenced by sensor cable length, which typically adds <2 Ω .
2. Resistances are approximate for a sensor temperature of 70 °F (21 °C).
3. Heater resistance range is 108- 120 Ω .
Note: There is added resistance to consider when measuring the flow element from the remote transmitter. The cable adds
extra resistance. The added resistance can be found by measuring the ACT SEN wire to the ACT EXC wire (e.g.,
TB1-4 to TB1-3.).
For Remote Units – If the measured values do not match that shown in the above table, unplug the cabling connecting the local enclosure
flow element to the remote transmitter and measure the resistance between the terminals of the flow element assembly terminal strip TS1.
Compare the measured values with the values shown in Table 29 below.
Table 29 – Flow Element Resistance (In Ohms) at the Local Enclosure
Term
Number
1 2 3 4 5 6 7 8
1 N/A 0
1
1080
2
1080
2
1080
2
1080
2
∞ ∞
2 0
1
N/A 1080
2
1080
2
1080
2
1080
2
∞ ∞
3 1080
2
1080
2
N/A 2160
2
0
1
2160
2
∞ ∞
4 1080
2
1080
2
2160
2
N/A 2160
2
0
1
∞ ∞
5 1080
2
1080
2
0
1
2160
2
N/A 2160
2
∞ ∞
6 1080
2
1080
2
2160
2
0
1
2160
2
N/A ∞ ∞
7 ∞ ∞ ∞ ∞ ∞ ∞ N/A 115
3
8 ∞ ∞ ∞ ∞ ∞ ∞ 115
3
N/A
Notes: 1. Theoretical zero-ohm table values are influenced by sensor cable length, which typically adds <2 Ω .
2. Resistances are approximate for a sensor temperature of 70 °F (21 °C).
3. Heater resistance range is 108- 120 Ω .
If the instrument has been on for some time, the resistance of the active RTD will be greater than the reference RTD.