CuVoodoo

the sorcery of copper

User Tools

Site Tools


ea-ps_2084-03b

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision
Previous revision
Next revisionBoth sides next revision
ea-ps_2084-03b [2015/05/26 18:06] – add documents kingkevinea-ps_2084-03b [2015/06/03 21:35] – experiments kingkevin
Line 33: Line 33:
   * [[http://www.elektroautomatik.de/files/eautomatik/treiber/ps2000b/programming_ps2000b.zip|programming manual]] ({{:ea-ps_2084-03b:programming_ps2000b.zip|archive}})   * [[http://www.elektroautomatik.de/files/eautomatik/treiber/ps2000b/programming_ps2000b.zip|programming manual]] ({{:ea-ps_2084-03b:programming_ps2000b.zip|archive}})
   * [[http://www.elektroautomatik.de/files/eautomatik/treiber/usb/usb_cdc_acm_driver.zip|driver]] (USB ACM for Windows)   * [[http://www.elektroautomatik.de/files/eautomatik/treiber/usb/usb_cdc_acm_driver.zip|driver]] (USB ACM for Windows)
-  * [[http://www.elektroautomatik.de/en/easyps2000-en.html|easyPS2000 software]] (Windows, [[http://www.elektroautomatik.de/en/easyps2000-en.html|demo only]])+  * [[http://www.elektroautomatik.de/en/easyps2000-en.html|easyPS2000 software]] (Windows, demo version) 
 + 
 +====== measurement ====== 
 + 
 +When powering the device on, I noticed that the voltage on the display did not change while I was turning on the knob. 
 +But the Digital Multi-Meter (DMM) actually shows that the voltage actually does change. 
 +Just the reading on the screen is inaccurate. 
 + 
 +It was time to measure how inaccurate this power supply is. 
 +But doing that manually just takes to long. 
 +So I decided to implement the protocol to control the the power supply, and I will measure the set output using a DMM connected to the computer. 
 + 
 +===== power supply ===== 
 + 
 +To control the power supply I implemented the protocol described in the {{:ea-ps_2084-03b:ps2000b_programming.pdf|programming manual}}. 
 +The source code is available on [[https://git.cuvoodoo.info/kingkevin/ea-ps_2084-03b/tree/master|git]]. 
 + 
 +The [[https://git.cuvoodoo.info/kingkevin/ea-ps_2084-03b/blob/master/control.rb|control]] programming will increment the voltage from 0 to 84 V in 0.1 V steps, at 1.0 A. 
 +It will set the voltage and current which are set, actual (measured by the power supply), and [[#mutlimeter|measured]] (measured by the DMM) 
 + 
 +===== multimeter ===== 
 + 
 +To measure the output of the power supply I used two [[http://uni-trend.com/UT61E.html|UNI-T UT61E]]. 
 +These are good multimeters for electronics which you can get [[http://www.aliexpress.com/wholesale?catId=0&SearchText=uni-t+ut61e|quite cheap]], with 22000 counts, and a connection to the PC. 
 +More functions and its accuracy are available in the [[http://uni-trend.com/manual2/UT61English.pdf|manual]] ({{:ea-ps_2084-03b:ut61english.pdf|archive}}). 
 + 
 +==== connection ==== 
 + 
 +The DMM comes with an RS232 [[http://www.uni-trend.com/en/product/2014_0626_553.html|UT-D02]] cable. 
 +To connect to the PC you need a RS232 to USB converter (are PCs with COM ports still manufactured?). 
 + 
 +The cheapest RS232 to USB converter one is based on the CH341 chip. 
 +Sadly the 7O1 mode used by the multimeter [[http://www.cnx-software.com/2015/03/07/sigrok-and-pulseview-in-ubuntu-14-04-with-uni-t-ut61e-digital-multimeter/|isn't supported]] by the linux driver. 
 +I also tried the [[https://github.com/karlp/linux/tree/ch341-3.18.6|patch]], and after toggling DTR I get wrong data out. 
 + 
 +I also has an old ARL3116 based RS232 to USB converter, but there too the mode didn't seem to be supported. 
 + 
 +Finally I found a FT232-based RS232 to USB converter. 
 +This is an expensive cable (but good quality), from an evil company, and it worked. 
 + 
 +But instead of using it, I decided to connect the cable to a CP2102-based UART to USB converter. 
 +Then you have to keep two things in mind: 
 +  * RS232 signals are between -12 to +12 V, while UART uses 0-5 V. This was solved by simply using the 5 V pin from the converter to power the cable. 
 +  * RS232 signals are inverted compared to UART. This was solved by inverting the signal using an NPN transistor and two resistors. 
 + 
 +More details about the cable and modification is described in this picture: 
 + 
 +For the second multimeter I used a [[http://www.uni-trend.com/en/product/2014_0626_555.html|UT-D04]] USB cable. 
 +This time the data doesn't come over a serial port, but rather a HID device. 
 + 
 +==== communication ==== 
 + 
 +To read the data from both multimeter I used [[http://sigrok.org/|sirgork]]. 
 +It supports the [[http://sigrok.org/wiki/UNI-T_UT61E|UNI-T UT61E]] and [[http://sigrok.org/wiki/Device_cables#UNI-T_UT-D02|both]] [[http://sigrok.org/wiki/Device_cables#UNI-T_UT-D04|cables]]. 
 + 
 +Once [[http://sigrok.org/wiki/Sigrok-cli|sigrok-cli]] installed you can record the data using the following command: 
 +<code> 
 +sigrok-cli --driver uni-t-ut61e-ser:conn=/dev/ttyUSB0 --samples 1 -O analog 
 +</code> 
 +or 
 +<code> 
 +sigrok-cli --driver uni-t-ut61e:conn=1a86.e008 --samples 1 -O analog 
 +</code> 
 +depending on the cable. 
 + 
 +====== experiments and results ====== 
 + 
 +I've run 5 experiments: 
 +  * go from 0 V to 84 V in 0.1 V increments, without any load 
 +  * go from 0 V to 84 V at 1.0 A in 0.1 V increments, with a 678 Ω load 
 +  * go from 0 V to 11 V at 1.0 A in 0.1 V increments, with a 10.2 Ω load 
 +  * go from 0 A to 3 A in 0.1 A increments, with a short 
 +  * go from 0 A to 1 A at 10 V in 0.01 A increments, with a 10.2 Ω load 
 + 
 +After changing a value I've waited 3 seconds for the measurements to stabilized. 
 + 
 +The measurements and accuracy calculations are available in this {{:ea-ps_2084-03b:accuracy.tar.gz|spreadsheet}}. 
 + 
 +Here are the resulting graphs: 
 +  * go from 0 V to 84 V in 0.1 V increments, without any load 
 +{{:ea-ps_2084-03b:voltage-no_load-difference.svg?900}} 
 +{{:ea-ps_2084-03b:voltage-no_load-set_accuracy.svg?900}} 
 +{{:ea-ps_2084-03b:voltage-no_load-nominal_accuracy.svg?900}} 
 +  * go from 0 V to 84 V at 1.0 A in 0.1 V increments, with a 678 Ω load 
 +{{:ea-ps_2084-03b:voltage-678_ohms-difference.svg?900}} 
 +{{:ea-ps_2084-03b:voltage-678_ohms-set_accuracy.svg?900}} 
 +{{:ea-ps_2084-03b:voltage-678_ohms-nominal_accuracy.svg?900}} 
 +  * go from 0 V to 11 V at 1.0 A in 0.1 V increments, with a 10.2 Ω load 
 +{{:ea-ps_2084-03b:voltage-10_ohms-difference.svg?900}} 
 +{{:ea-ps_2084-03b:voltage-10_ohms-set_accuracy.svg?900}} 
 +{{:ea-ps_2084-03b:voltage-10_ohms-nominal_accuracy.svg?900}} 
 +  * go from 0 A to 3 A in 0.1 A increments, with a short 
 +{{:ea-ps_2084-03b:current-short-difference.svg?900}} 
 +{{:ea-ps_2084-03b:current-short-set_accuracy.svg?900}} 
 +{{:ea-ps_2084-03b:current-short-nominal_accuracy.svg?900}} 
 +  * go from 0 A to 1 A at 10 V in 0.01 A increments, with a 10.2 Ω load 
 +{{:ea-ps_2084-03b:current-10_ohms-difference.svg?900}} 
 +{{:ea-ps_2084-03b:current-10_ohms-set_accuracy.svg?900}} 
 +{{:ea-ps_2084-03b:current-10_ohms-nominal_accuracy.svg?900}} 
 + 
 +As you can see the measured values are most of the time higher than the set values, but within the 0.2 % accuracy (to 84V or 3A)
 +But the actual values displayed by the power supply is way below what is set, and outside of the accuracy, particularly on the low voltages. 
 + 
 +Conclusion: don't trust the displayed voltage (it's too low), but you can be confident the output is right (except for the very low voltages and currents).
ea-ps_2084-03b.txt · Last modified: 2024/01/07 17:49 by 127.0.0.1