SCC CARD IN CEL SSDAC

 Signal Conditioning Card  (SCC)

1) There are two SCC cards in SSDAC. 

2) SCC 1 is connected to TX 1 and RX 1 coils.

3) SCC 2 is connected to TX 2 and RX 2 coils.

4) SCC 1 generates carrier signal 21 KHz and feed it to TX 1 Coil. RX 1 receives this signal and send back to SCC 1 Card.

5) SCC 2 generates carrier signal 23 KHz and feed it to TX 2 Coil. RX 2 receives this signal and send back to SCC 2 Card.

When there is no train there is a phase difference of 180 degree between the signals of TX and RX coil.

This phase shift can be monitored by means measuring 2.2 V DC if there is no wheel on device.The range is 2.0 to 2.5 volts.

If this voltage is in the range,it means that SCC card is transmitting correct frequency, receiving  correct frequency and phase difference between  Tx and Rx are 180 degree.

If during installation of SSDAC you are not getting this 2.2 V DC, reverse the RX Cable polarity in Location box for getting the same.

When you place Dummy wheel on the track device the phase difference between signals of Tx and Rx coils becomes almost zero and  this voltage should be less than 0.7 volts DC.

SCC card demodulates the signal received from Rx.

After Demodulation, it produces a 5 volt digital pulse which is forwarded to both MLB 1 and MLB 2 for processing. 

There is no point to check this 5 Volt anywhere in unit or in Location Box.At the time of failure ,we can not check whether SCC Card is forwarding this 5 volt to MLB Cards or not.


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