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| Tektronix A622 current probes - el (not so) cheapo clones. |
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| shakalnokturn:
A bit late I think but just for the records: No measurable current draw in OFF position. Draws 7mA @ 8.5V when on. I have one of these with a dead hall sensor (one terminal open). In the technical documentation provided above the hall sensor is identified (in the schematic only, not in part list) as a HW-300B-E (AKM). I ordered and received some of these from Aliexpress, they look genuine perform like linear hall sensors, marking and package dimensions conform to the attached AKM datasheet. However the hall sensor originally fitted to the current probe does not have the same dimensions, it's 2.7x 2.3x 0.9mm where the AKM part is 2.7x 2.9x 1.65mm. Original sensor has nothing readable on it (but it was held in glue) one side is coloured blue. The sensor is sandwiched in a plastic housing that then fits into the magnetic core, it's all a very tight fit so I've had to sand two sides of the sensor to get the whole assembly to fit back into the core. Now the clamp is working but I have too much gain even with the multi-turn trimmer at minimum so I'm going to have to work around that too... So I don't really believe that they used the part number stated in the schematic, at least not on all models... Any clue what other sensor they may have used ? |
| shakalnokturn:
I ended up changing the gain at the differential amplifier to get the gain trimmer back in a useable range. Readjusted at DC, then thought it would be interesting to see how it performed in AC. Test setup is a function generator into a HK6150 audio amplifier with 10 Ohms worth of load. Channel 1 yellow: 1 Ohm resistor for reference measurements. Channel 2 cyan: LEM HEME PR30 (first edition with only 100mV/A position) Channel 3 magenta: Stock Tek A622 Channel 4 green: Repaired Tek A622 I pushed this about as far as the audio amplifier would go just to see how the PR30 would cope. The main conclusion is that the PR30 doesn't rely solely on a hall sensor... |
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