Important general considerations
Great care must be taken when adding datalogging to railway signalling systems.
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Measurement type | Current clamp | Rating | No of turns | ||
|---|---|---|---|---|---|
DC track circuits | Rowe Hankins NIC361-6A | 600mA DC | 1 | ||
AC track circuits | Northern Design XD-I420-1 | 5A AC | 5MPEC VTi21 | 1A to 100A AC | 1 |
Points motor current | LEM PointSenz PCM20P | 20A DC | 1 |
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- 250mA fuses must be inserted in each leg between the voltage being monitored and the transducer.
| Note |
|---|
Note that: B50/B24 is usually full wave rectified unsmoothed, so the peak voltage is actually 50 x 1.41 = 70V, and 24 x 1.41 = 34V. |
Recommended transducers:
Measurement type | Transducer | Rating |
|---|---|---|
AC points motor voltage, BX110 | Omega DRA-ACT-2V-1 | 150Vac |
B50, B24 | Omega CCT-01-0/100V | 100Vdc |
DC points motor voltage | Omega CCT-01-0/650V | 650Vdc |
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- The voltage transducer must contain 3-way isolation to a minimum of 4M Ohms at 250V between input, output and housing.
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Trackwork and point machines
Possible applications:
- Rail temperature
- Rail vibration
- Points load pin
- Clamp lock power pack monitoring
- Points position monitoring
| Warning |
|---|
Special care must be taken when attaching sensors to rails, pointwork, point machines or anything electrically connected to them. |
Sensor requirements:
- Each sensor must have electrical isolation between the 4-20mA output and the trackwork to a minimum of 4M Ohms at 250V.
- 250mA fuses must be provided in each leg of the current loop.
- Only Network Rail approved points load pins may be used.
- When monitoring the pressure in clamp lock power packs, only pressure sensors approved by the manufacturer of the power pack must be used.
- Where sensors are attached to both rails, a risk assessment must be carried out to ensure that there is no risk of a track circuit being false fed
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Other measurements
The 4-20mA analogue input card can be used with many other transducers, including temperature, pressure etc.
Parameter | Suggested 4-20mA device |
|---|---|
Temperature | Phoenix Contact MINI MCR-SL-TC-UI(-NC) |
Strain / force | Strainstall provide a wide range of sensors for measuring force in many different situations. |
Flow | Omega FMG203-NPT |
Wind speed | Vector Instruments (4-20mA special order) |