MCC 128 input impedance question

[NicR]

I have a MCC-128 and want to acquire data from an AT 50 B10 current transformer. The MCC 128 data sheet says the input impedance is 2 GΩ and the AT data sheet says the output load should be > 2 MΩ. Am I correct in thinking that I can just wire the AT up to one of the MCC analogue inputs?

[JRys]

Hello,

2 MΩ is considered high source impedance which causes measurement errors. The MCC 128 channels share a single A/D converter, each taking a turn. When a channel is selected, a small charge from the previous channel is transferred. If all the channels are connected to low-impedance sources (< 100), the charge dissipates, letting the source charge the input to the real value. However, a high-impedance source cannot dissipate the charge and gets added or subtracted from the real value.  If the current transformer is the only channel being read, it doesn't matter. The current sensor outputs a significant signal (0-10v), and depending on the other channels, the error caused by the high impedance may be small enough to ignore. 

Best regards,
John

[NicR]

Thanks John, I'll only be reading one channel so hopefully this will be fine.