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--- ea-ps_2084-03b [2015/05/27 18:47] – typo kingkevin
+++ ea-ps_2084-03b [2015/06/03 21:35] – experiments kingkevin
@@ Line 79: / Line 79: @@
 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).