adccommunitymod (AutomationDirect) asked a question.
Created Date: March 08,2008
Created By: jimmycash
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Hi, I just bought an FC-33 conditioner to use in a 405 PLC setup to program a Sorensen DCS supply to a negative voltage. I normally just program them from zero to full scale with the 0-5v right out of the DAC when they are being used as positive output supplies. When used as negative supplies they must be programmed with a current source because the supply's control circuits are tied to the negative output buss which will now be floating at whatever voltage the supply is programmed to. In this case it's a 0 to 40 volt supply. To develop the 0 to 5 volt programming signal I'm using the 0 to 20 ma output of the FC33 across a 249 ohm precision resistor.So far it's all working fine on the bench with the following exception - I can't get a full 20 ma out of the FC33, only 19.6 ma and with the 249 ohm resistor it only develops 4.88 programming volts which doesn't drive the supply to full scale. I know I can get around this putting a small pot in series with the resistor but I'd rather not have to go that way. From reading the FC33 specs I'm lead to believe that it's 20ma output can be adjusted up to a max of 21 ma. I 've tried the input cal procedure and can change the point where the module's output stops increasing and that part works ok. Instead of it stopping at 5.0 volts I was able to cal it at 4.95 and 5.05 volts but it still only outputs 19.6 ma. Does anybody know how, if possible, I can get it to output 20.1 ma so I get exactly 5.00 volts across the 249 resistor with exactly 5.00 volts in?
Created Date: March 08,2008
Created by: jimmycash
Hi,
I just bought an FC-33 conditioner to use in a 405 PLC setup to program a Sorensen DCS supply to a negative voltage.
I normally just program them from zero to full scale with the 0-5v right out of the DAC when they are being used as positive output supplies.
When used as negative supplies they must be programmed with a current source because the supply's control circuits are tied to the negative output buss which will now be floating at whatever voltage the supply is programmed to. In this case it's a 0 to 40 volt supply.
To develop the 0 to 5 volt programming signal I'm using the 0 to 20 ma output of the FC33 across a 249 ohm precision resistor.So far it's all working fine on the bench with the following exception - I can't get a full 20 ma out of the FC33, only 19.6 ma and with the 249 ohm resistor it
only develops 4.88 programming volts which doesn't drive the supply to full scale.
I know I can get around this putting a small pot in series with the resistor but I'd rather not have to go that way.
From reading the FC33 specs I'm lead to believe that it's 20ma output can be adjusted up to a max of 21 ma. I 've tried the input cal procedure
and can change the point where the module's output stops increasing and that part works ok. Instead of it stopping at 5.0 volts I was able to cal it at 4.95 and 5.05 volts but it still only outputs 19.6 ma.
Does anybody know how, if possible, I can get it to output 20.1 ma so I get exactly 5.00 volts across the 249 resistor with exactly 5.00 volts in?