When there were real Teletype machines on line it was not unusual to see=20
100 volts on an open line. Add in the inductive spikes and it got more=20
interesting. I hope there are more reasonable specs today.
On 6/28/2013 8:48 AM, Matt Rhys-Roberts wrote:
> In the world of 4-20mA instrumentation, is there any such thing as a
> typical or ideal input resistor at the receiver end?
>
> I notice a few diagrams using a 250R res across the Rx input terminals,
> which seems a default value. To some extent I guess it can be altered to
> provide the required voltage from the current range.
>
> It seems that I need to specify enough voltage at the Tx end, to
> overcome both the cable's length and the Rx's Zin. Both these
> resistances are a little undefined to me at this point.
>
> Any personal experiences about this please?
>
> Regards,
> Matt.

--=20
John Ferrell W8CCW
"The pessimist complains about the wind;
The optimist expects it to change;
The realist adjusts the sails."
      William A. Ward


--=20
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