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Has anyone got any suggestions for a current clamp with a BNC connection so that I can record currents on an oscilloscope? Does the sensitivity make a difference, so would one that is 100 mV / A be better than one that is 10 mV / A?
Can't say I have ever seen a current clamp with bnc connectors. Usually they have test leads to plug into a DVOM. You might use something like this. Probably a little digging will get the proper gender needed.
If you need to measure DC, the run of the mill current clamp won't work. They are essentially half of a transformer, magnetically coupled to the AC field around the wire.
AC/DC current clamps exist, but they are active devices using Hall effect sensors to measure the field whether it's AC or DC. DC measurements can be a bit tricky, and may require zeroing the current clamp with no current flow to compensate for the external magnetic field.
The only problem is that we have to calibrate them every year then the first thing a technician seems to do is turn the knob on the front which puts it out of cal ......
The only problem is that we have to calibrate them every year then the first thing a technician seems to do is turn the knob on the front which puts it out of cal ......
How can a calibrated item have a customer adjustment to destroy the calibration on the front? - not that yearly calibration isn't just a money making scam anyway
The only problem is that we have to calibrate them every year then the first thing a technician seems to do is turn the knob on the front which puts it out of cal ......
I give up: From the manual: Zero Adjustment The output zero offset voltage of the probe may change due to thermal shifts and other environmental conditions. To adjust the output voltage to zero, depress the thumbwheel and rotate. Ensure that the probe is away from the current carrying conductor whilst the adjustment is made.
It's really part of the operation and the operator should know when to adjust them. e.g. It doesn't read close to zero.
If your that worried, make a at least 3 calibrators or something. Why 3, you compare them against each other.
For sunlight intensity measurements we had two standards measured. The equivalent of NIST. Then we calibrated 10 standards of our own. Every day we used two standards to calibrate our light source. The one we used yesterday and a new one. When a lamp got changed, about every 1000 hrs we had to use 3. As the lamp aged, the spectrum changed. It had less blue light. You have power to the lamp and measured and controlled intensity.
I never worked at a place where you had to use keys and process protection methods. In fact, one of our temperature controllers was annoying. You had a manual and a configuration manual. Configs required a plastic key.
To be fair, when you balance them on an engine doing 5000RPM and 900+NM for hours/days on end, things tend to vibrate out of cal anyway.
The best current clamps we had were the ones we custom made out of AC clamps with ferrite cores in. We machined out the ferrite enough for an Allegro linear hall sensor and made some small boards to fit in the shell and condition the signal. The engineers were more interested in events and waveform shapes (i.e. ignition coil currents) than accuract although they were pretty accurate. They were used to trigger recording and events and came in at around £15 per clamp (plus a bit of labour) vs the £450+ of a calibrated clamp meter. They were lighter and for some reason didn't melt as easily .....
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