The spec/accuracy within the 0-200 A range is +/-1% of reading +/- 100mA.
You will not be able to measure small currents, eg battery drain. Nevertheless, when buying just one current clamp you made the right call with the TA 167 imo.
It will work for allmost everything from fuel injectors to starter motors.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Well originally i thought so to. Especially since the main reason i need one is for relative compression tests , but I've seen multiple sources use a low current probe for this. Probes claims30- 60a max but they're mapping 200-300amp+ on the scope. One video the guy had a low current probe.on the negative cable another had it on the b+ to starter cable with a 2v scale on the scope. So what gives ? Can they measure past 60a just not accurately? If you can put a low amp clamp on the negative cable then why does everyone clip the battery to starter cable seems like negative would be the way better option
As current flow is the same through the entire circuit it does not matter where you connect to, be it the positive or the negative leg.In the real world it mainly depends on how easy you get to one side or the other...
Most of the 60 A low current probes will give considerably higher readings, some up to allmost 200 amps. Are these readings accurate? Probably not, but who cares if you're doing a relative compression test.... Some low amp probes have small jaws not allowing to put them around a fat cable properly.
Another option is to AC-couple a low current amp clamp. That way it stays within its designed current range.
Yet another way is doing RC by voltage/voltage drop measurement: connect your signal lead to the block ground and the ground lead to B- to get a signature. Adjust to 500mV or 1 V per screen. The voltage peaks represent directly the compression humps.
Or connect your scope across the battery, ac-coupled. This capture will show the compression humps inverted, the voltage drops(valleys) correspond to the TDC's.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Especially since the main reason i need one is for relative compression tests , but I've seen multiple sources use a low current probe for this.
Nah, you made the right call. I used an AESWave low amp probe to do relative compression for many years. It worked, but there were always hassles. Many engines exceeded the 200A max of the probe. The small jaws were a huge pain to get onto some cables. Finally getting a high amp probe changed my life.
If you can put a low amp clamp on the negative cable then why does everyone clip the battery to starter cable seems like negative would be the way better option
Good question? I usually do go to the negative side, if only because there's fewer cables to choose from. :silly:
Can they measure past 60a just not accurately?
I don't know that I ever compared them. :huh: Might try that this week.
I'm a scope newbie can you explain a few things. What does a/c coupling do? And can you explain how you get a signal from connecting to block and b- and also if you are using a low amp probe putting it in the negative cable wouldn't the current be much lower because it's after the load?
[quote="What does a/c coupling do? And can you explain how you get a signal from connecting to block and b- and also if you are using a low amp probe putting it in the negative cable wouldn't the current be much lower because it's after the load?[/quote]
A/C (alternate current) coupling will take off the DC (direct current) portion of any waveform. As practical result you will have a higher resolution..An ac- coupled RC cranking test will only show the peak to peak range , eliminating from the signal the base current flow thru the starter.
Current flow is the same in any part of the circuit. No matter wether before the load or after the load. It's a "what goes up must come down", like thing, all the electrons leaving one battery terminal MUST make it back to the other terminal.
On the other hand voltage (you can figure it as electric pressure) will change/diminish while current travels through the circuit. Obviously the voltage should be dropped (used/consumed...) over the consumer we want to do the desired work, in this case the starter.
But everything else in a working circuit - a fuse, a conducter, a switch, a connecter etc - also requires some voltages/ electric pressure to let the current flow thru it.
So when we dispose of 12 volts of electric pressure the mayor part of it should fall/drop over the spinning starter but there is still a tiny rest of electric pressure left to overcome the resistance in the rest of the circuit - from the starter housing back to the negative battery post.
This voltage is what you can measure when connecting to engine block and battery minus. The starter consumes more amps/higher currents on the compression strokes. Higher currents require a higher electrical pressure = voltage to get pushed through this remaining portion of the circuit. When not on a compression stroke the required current to spin is slightly less and so is the necessary voltage to bring the electrons back home to B-.
So the voltage on the ground side of the starter is a true representation of the current flow and it will show you the relative compression just as the current does.
Because of the high currents you may have to filter the signal in occasions.
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Topic Author
I used an AESWave low amp probe to do relative compression for many years. It worked, but there were always hassles. Many engines exceeded the 200A max of the probe. The small jaws were a huge pain to get onto some cables. Finally getting a high amp probe changed my life.