Can I modify a cheap current clamp to have a bigger resolution? (example, from 1A to 200A, to 0.1A to 600A)?
>>1013770
Short answer: no.
You /can/ get a low ratio current transformer (try EBay) and run the secondary through your meter. You'll add a small amount of error to your reading, but it's really the only way.
>>1013786
Also, the problem with CTs is they take a certain amount of energy to excite. This means that if you use a 3:1, 600A CT (to read 600A on your 200A meter) it might not be able to give you a reading at 0.1A and if it did there error would be huge because your meter is going to see 0.03A So you'd be better off getting a higher accuracy low current meter for that.
>>1013788
If you're a diyer there a few cheaper options, but I shill out for Fluke because nothing else lasts on my worksites as long. If you get an 87 or similar you can use the internal current module for everything <10A with high accuracy and decent resolution down to the microamp, and then plug in the clamp ("IC2" or something like that) for everything <800A.
>>1013770
as i recall if you wrap the wire around the clamp meter several times it will multiply the registered amps by the number of turns.
>>1013971
This
>>1013971
That'll work on the low end, and only if it's wires that you can unland long enough wrap around the probe. Still can't read 600A on a 200A meter without a CT though. But I like that idea.
>>1013770
>Can I modify a cheap current clamp to have a bigger resolution? (example, from 1A to 200A, to 0.1A to 600A)?
Prolly not worth the effort, really. You would be limited to the existing number of counts on each range, so it would be less accurate (it would have a detection interval only every 3 amps,,,).
The DMM thread (gone now) and a recent purchase (a Mega328 ESR meter) got me to pondering the possibilities of building your own DMM...
To measure volts--the main parts of a DMM are -basically- an ADC, a resistor ladder and a display driver
To measure ohms, you also need a reference voltage source
You could just use a clamp/hall sensors to measure amps (instead of using the probes at all) and avoid a major source of DMM mishaps
You could use a 16-bit ADC and get full ~65K count (using ALL the digits possible) on all scales
For the capacitance scale, you could integrate the ESR meter capacitance function, showing ESR and leakage
For the inductor scale, you could detect the inductor value as well as have a ringer function, to diagnose short turns in motor windings
You could have a number of frequency rates to check the capacitance and inductance at
You could have a few different impedance values for checking resistors at (selectable, or auto-select...)
For the display, you could have a regular LCD showing the usual number value, plus you could have a TFT screen showing a graphing display with different modes
For logic probing, you could have several different continuity/voltage beeps (say, a different tone of note for 0-1, 1-2, 2-3, 3-4 and 4-5 volts)
For PWM issues, you could have a PWM generator on-board, and then monitor the output in the TFT screen
For the resistor ladder, you could apply corrections in the software, instead of needing a super-precise resistor dividing network....
It could be pretty impressive.
>>1014577
>Less accurate
500 amps is no joke, but dont get me started on 501.
I'd take a meter that had a +-3 amp reading but it would have to also read lower amps accurately.
>>1014730
From what I've read, it would probably be safer to have a big clamp meter for measuring from 1-and-above amps, and then have a cheap multimeter for measuring <1 amp directly....
The high amps setting seems to be a common weakness of cheap DMMs, but even the cheapest ones measure (lower) volts, amps and ohms pretty well.
To measure up to 1000 volts cheaply, you could just make a voltage divider from ten resistors of 50k or so and get the volts off one resistor....
