fluke PM2813 problem - please help me  - Page 1
Forum section: electronics / testgear

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 13, 2013, 08:52:33 pm
content: heyso as some of you know I've purchased the PM2813 , great PS in all means , but ther's some problem with it , the sensing is bad , let me explainso I've got some binding posts for the 3 channels plus the sensing ports , I've drilled the front panel and all fit nicely , so I turned the PS on and connected one of the Channels to my DC load , set to 20V 3A , draw 2.99 ( 3A will turn the PS into the CC mode ) , and obviously ther's dropp of the wires , so obviously you connect the sensing leads right ? I did so , but the voltage wasn't 20V . without the Sensing it was say 19.7V and with the sensing it was 19.8V , so what's wrong ? well ther's shorting bars on the rear connectors between the + and S+ and the - and S- , so I've disconnected them , and turned the PS on , BUT there was written " CH1 FAIL " , WTF ?well I thought there is no internal 100ohm resistors between the sensing and output , so I put some , but the "FAIL" is still there ( Yes I have restarted the PS )so please , can someone can spot me the problem ?thank you in advance !

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 14, 2013, 11:24:21 am
content: someone ?

author: dr_p
author_rank: Frequent Contributor
timestamp: May 14, 2013, 12:40:27 pm
content: is it set to local sense?

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 14, 2013, 12:44:22 pm
content: heyfirstly _ thank youso if it does set to loacl . how shall I set it to remote ?if you mean the jumpers inside , I have already turn them to the "on" position

author: PA4TIM
author_rank: Super Contributor
timestamp: May 14, 2013, 05:24:01 pm
content: I have a P2811, the same psu but only one channel ( firmware seems to be equal)Did you do the calibration ? Mine was not accurate before I did that. ( Voltage was off and -40 mA without sourcing current after following the manual, ( the resistor thing) then I did what looked more logical to me and used my Keithley 2000 to measure current and now it is spot on)On my 2811 the 4 terminals on the back are connected to 4 bannana busses on the front ( original option in a sub chassis under the psu, I added a powerswitch there)There is a switch beside the bannanas that lets me choose between sense and no sense. It just couples the sense to source lines. There are no resistors. It gives an error if I set the switch wrong. ( and sense is not connected) looks like that is your problem. If I understand right you modified it from back connectors only to front connectors ?)The sense is part of the feedback. It measures the voltage and regulates the output according. I know because that was the problem on mine. Without the sense it sees no output.If I remember well during repair: If you put an external voltage on the sense lines you get that as a reading on the display. So the display seems to shows the real output and not the set output ( and that is a safe idea) So that could imply you should see a lower reading using sense and long wires. However I would expect it to regulate voltage again to setting by itself. But I have never checked that. Never used the sense. If you see the set value minus the voltdrop there could be a problem in the feedback. Is the output correct using a multimeter ?I can try some tests on mine if you want.http://www.pa4tim.nl/?p=3584my PM2811, so you can see the switch

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 14, 2013, 06:14:08 pm
content: heyupdate :problem solved ! , one power supply is solved , one more to go ! ( If someone follows me )I mistakely connected the sens wrong ( output 3 to uutput 1 , and vice versa ) the rear terminals are opposite to the front , hence the mistake ,I also connected 10ohm resistors from S+ to V+ and S- to V- , due to "fail" written when the sense are not shorted to the output terminals ,now all fine , I've tested 6V at 10A , all works fine , but when using the sense ther's problem , the PS cannot output more then 1V above the set value ( in order to compensate for wier losses ) , so ther's need to use heafty banana connectors ( mine dropped 200mV just accross the banana connectors ) so I had one big banana plug and he did well there ,the problem with that PS is when "FAIL" appears on the screen , you cant tell what has fail , you have to know by yourself , it is "smart" supply , why can't they write " eror XX" instead ? , so that on the menual you'll be able to se , "eror 41" will mean , too much drop on wiers , and such ,mine HP34401 tells me " 0.021mVRMS" when I measure ACV , I am sure the output ripple is more like 1mVRMS or so , but does someone know what is the ripple under 10A ?my scope tells me 21mVpp ( Ie rughly 10mVRMS ) , can someone confirm ? ( 20Mhz BW limit on )thank you