Mas01

Many thanks for taking the time to reply. I appreciate it. I wish I were clued up about PLCs then my terminology would not be so confusing. To answer your question about the analogue input...basically there is a pressure sensor on the vessel which sends a mA current to the PLC and this is 'mapped' to D40. If I understand the ladder logic correctly (I think I do now, thanks to the above help), the current is multiplied by 7,502 and then the result is divided by 10,000. The resulting (analogue) current is output by the PLC (D582) and interpreted by the little digital display which tells us the pressure (units Torr) inside the vessel. Many thanks again - I feel totally lost sometimes.

Thanks but I’m confused. I know that D582 is an  analogue output (mA) which is used to drive a little digital display of the vessel pressure. Does this mean the value on the display is not accurate?

UPDATE...I think the penny has dropped....because after this line 1265   |---------| |----------[*   D40    K7502   D580 ]   I see -----------------------------[D/   D580    K10000     D582   ]   which is a DIVISION by 10,000, (right?) and then deposit the value in D582 (vessel pressure)   D582 I know is an analogue output of mA.

Brilliant - I thought K7502 was some mysterious variable name!! So it's the Decimal value 7502. This value makes sense because the Vessel Press D40 is being converted to TORR. Many thanks, I finally understood something!

Thanks again . I "enabled" some views and some of the parameter names appear in green, but nothing for K7502  or D580. If I can just find out the value of K7502 and D580, I will be happy. If "K" signifies a decimal number, what does "D" signify please?

Brilliant Gambit many thanks... on GX developer, when I hover over "D40" it tells me what it is "Vessel Pressure", but hovering over the others does nothing ....how can I find out what the other are? Totally lost, but many thanks for the reply.

Complete newbie thrown in at the deep end, please can someone tell me what the * means in this rung and what rung is trying to do? Thanks   1265   |---------| |----------[*   D40    K7502   D580 ]