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+--- Thread: Erratic Current measurements (/showthread.php?tid=1287)
Erratic Current measurements - luisgepeto - 24.02.2018
I am not able of getting consistent current readings.
I am using 4 different split core current transformers and attached them to the same cable that is powering up my pc so that ideally I have the same readings across all the SmartPi inputs. I am not measuring voltage and my RaspberryPi is powered up by a usb cable attached to the wall socket . Also the pins on my smartpi that are directly above my sensor inputs do not have any jumper installed except for I4 (not sure whether this is the correct installation - i removed the jumper for the picture)
I have also made sure that the contents of the file in /etc/smartpi have the following keys:
ct_type_1 = YHDC_SCT013
ct_type_2 = YHDC_SCT013
ct_type_3 = YHDC_SCT013
ct_type_4 = YHDC_SCT013
ct_type_1_primary_current = 100
ct_type_2_primary_current = 100
ct_type_3_primary_current = 100
ct_type_4_primary_current = 100
The two tests that I carried out were the following:
1. Make a full rotation of the connected current sensors connected to the smartpi i.e. I1 -> I2, I2 -> I3, I3 -> I4, I4-> I1 and so on. With this test I wanted to check if the result for each current sensor was consistent across inputs.
2. Make a full rotation of the clamps on the target measurement without changing the sensors connection (should not affect measurement)
However once I start the smartpireadout program I am not able to get the same value for all four current transformers.
Amongst the issues I have seen the following:
1. Measured current has differen values on every phase.
2. I4 input is the only one with the jumper installed on its jumper pins. This causes the reading to allways be a negative negligible value
3. The change_current_direction_X flag doesnt change the current sign, doesnt matter if set to 0 or 1
4. Rotating the clamp position along the same conductor renders different current measurements (no idea why this is happening)
These are the results for my tests
========= CONNECTION ROTATION 1 =========
I1: 1.6912797688692927 I2: 0.514815652681119 I3: 2.2674108816131033 I4: -0.05206709488183494
========= CONNECTION ROTATION 2 =========
I1: 0.06681043028378475 I2: 1.6093356501077427 I3: 0.5131641588988232 I4: -0.0834154495857771
========= CONNECTION ROTATION 3 =========
I1: 2.111149542648242 I2: 0.07515798067429807 I3: 1.6693899694639536 I4: -0.0578022823803531
========= CONNECTION ROTATION 4 =========
I1: 0.4911242236950937 I2: 2.190541352837153 I3: 0.08903052844558285 I4: -0.05125636157052611
========= CONNECTION ROTATION 5 (MATCHES CONNECTION ROTATION 1)/ CLAMP ROTATION 1 =========
I1: 1.3731720392394429 I2: 0.3151350408217172 I3: 2.119587174517789 I4: -0.06693053892249717
========= CLAMP ROTATION 2 =========
I1: 2.0377931915546306 I2: 0.9799964104143295 I3: 2.0613945390616215 I4: -0.07572849670818207
========= CLAMP ROTATION 3 =========
I1: 1.1113652340060411 I2: 0.7465652710767372 I3: 2.000499459234423 I4: -0.07077401536129468
========= CLAMP ROTATION 4 =========
I1: 1.0695674277341183 I2: 0.013782466292250427 I3: -0.004444019632359615 I4: -0.0753081164726886
========= CLAMP ROTATION 5 =========
I1: 3.326889183695378 I2: 0.20892897704025812 I3: 0.46749284902842464 I4: -0.07894140279373937
Do you have any idea why this is happening?
Greetings
Luis.
RE: Erratic Current measurements - jens - 15.03.2018
Hello Luis,
for the SCT013 please set the jumpers to 50mA. This is described in the manual. Otherwise please look at the attached picture.
The jumpers must be set in the relay direction.
[attachment=87]
Best regards Jens
RE: Erratic Current measurements - jens - 15.03.2018
Attached the manual.