Page Comparison

Point Machine

Motor Current

LEM PCM20P/SP2

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A “uni-directional” “4-wire” current clamp. It is designed to measure “positive current” only between 0 and 20 Amps, AC or DC, however due to the 4-20mA nature, the sensor will read as low as -5 Amps at 0mA output. The split core means it is possible to install without disturbing existing wiring.

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Note that when designing and installing these sensors, “conventional current flow” must follow the arrow on the sensor enclosure. E.g. for a positive sensor output, current flow in the measured conductor flows from in the direction of the arrow.

Many electrically driven switch machines can get away with using a single LEM PCM20 sensor. The designer must ensure that all motor current carrying conductors pass through the sensor in the correct direction. This arrangement depending on the machine type and number of feeds.

In some scenarios there may be no spare relay contacts available to trigger a capture and maintain direction of movement information. In such scenarios you may employ two LEM PCM20P sensors, which each sensor capturing switch motor performance for a single direction of movement.

LEM PCM30P/SP2

A “bi-directional” “4-wire” current clamp. It is designed to measure “positive and negative current” between -30 and +30 Amps, AC or DC, however due to the 4-20mA nature, the sensor will read as low as -45 Amps at 0mA output. The split core means it is possible to install without disturbing existing wiring.

Note that when designing and installing these sensors, “positive conventional current flow” must follow the arrow on the sensor enclosure. E.g. for a positive sensor output, current flow in the measured conductor flows from in the direction of the arrow. When current flow in the measured conductor opposes the arrow. negative output is generated.

Many electrically driven switch machines can get away with using a single LEM PCM30 sensor to both trigger and capture switch motor performance in both normal to reverse and reverse directions. The designer must ensure that all motor current carrying conductors pass through the sensor in the correct direction. This arrangement depending on the machine type and number of feeds.

Hydraulic Pressure

The range of clamp-lock style switch machines manufactured by SPX typically feature two in-built pressure transducers installed at the manifold outlet of the “normal” and “reverse” drive hoses. One of these sensors will output signal during “normal” movement of the switch, whilst the other sensor will output a signal during the “reverse” movement of the switch. This is useful, as it means that direction information triggers may be obtained from these sensors without the need to monitor interface relays or valve feed circuits. Pressure is reported on a scale of 0 to 120 bar. Both transducers require monitoring for each switch machine.

Note the sensor is “loop powered” only requiring two-wire operation.

Valve / Relay Feeds

NIC-RI-361BB

Sometimes, there may be no mean obtaining direction of motion of a switch machine from motor current sensors alone

• Motor always turns in the same direction, and no relays are available

• LEM PCM30P sensors are unavailable, and there are no accessible relay contacts.

In such instances it is possible to use the NIC-RI361BB sensor to provide a “fake” relay input to a data logger.

This current sensor features a volt-free-contact output that operates at 60 mA. This can be used to generate a digital trigger signal from an otherwise analogue reading. The signal could be from a relay coil, where no spare contacts are available, or from the solenoid valve feeds of hydraulic switch machine equipment. The sensor has no split core meaning, that existing wiring must be disconnected and rerouted thorough the sensor aperture.

DC Track Circuits

Track Circuit Current

NIC-RI-361BD

The 4-20 mA range of this 4-wire sensor is 0 to +600 mA. This makes it ideal for monitoring DC track circuit current in most applications. They are typically fitted at the relay end, but some times at the feed end also. The sensor has no split core meaning, that existing wiring must be disconnected and rerouted thorough the sensor aperture.

Note that when designing and installing these sensors, “positive conventional current flow” must follow the arrow on the sensor enclosure. E.g. for a positive sensor output, current flow in the measured conductor flows from in the direction of the arrow. When current flow in the measured conductor opposes the arrow. negative output is generated.