Isn't it nice when a client says...and use THIS sensor (none other), to turn on
 and off
your stuff (i.e., an inhibit TTL signal).  Well, as it happens to be, the output
 of
this particular level sensor is 4-20mA.  When it reaches a certain level in a
 tank, the
output is in that form (low level is 4mA, high level is 20mA).  So, at 20mA, we
 are supposed
to inhibit our stuff from running. Simple..done it before, but either with a PLC
 or a hard
contact.  Sorry to bore you all with this....

SO...rather than reinvent the world, has anyone built a circuit, doesn't have to
 be PIC based
exactly, to monitor a 4-20mA loop and just switch a TTL signal when it reaches
 20mA? Yea, I
could build a window detector, or use a ADC and PIC, but time is a problem so
 just need a simple
and inexpensive solution.  Otherwise, I can use a couple LM311's and such...

Private mail is fine to save on bandwidth.  hcooper@es.com