So I've ordered a scope, Labnations something or other, and I want to get an amp clamp as well. My question is should I get a low amp clamp or a high amp clamp? Figure I need a high amp clamp to do relative compression test but concerned I won't be able to read small currents with a high amp clamp? Can I use a low amp clamp with a 20:1 attenuator for relative compression? Going to get one of the Hantek ones as they're cheap but open to others if there is justification for it. Just DIY guy so I don't want to spend a fortune.
Thanks for any help.
Congratulations on getting your scope! Personally, I'd get a low amp probe first, and worry about the high amp probe later (or never). I've always used a low amp probe for relative compression on gasoline engines, and never had any problems. Diesel is another story, due to higher starter current draw.
Tyler wrote: Congratulations on getting your scope! Personally, I'd get a low amp probe first, and worry about the high amp probe later (or never). I've always used a low amp probe for relative compression on gasoline engines, and never had any problems. Diesel is another story, due to higher starter current draw.
Sorry if I wasn't clear on that one. :blush: Was referring to the relative compression scope trace, the green line on the scope capture.
Can you link me to the Hantek clamp you were looking at? The other consideration with low amp probes and relative compression testing is the inside diameter of the jaws. You want as wide as possible to fit around thick battery cables, or you won't get an accurate reading. The AESWave clamp measures out at just over 9mm.
Hantek one is the same, 9mm. That was a concern as well. Here's a link to the Hantek website.
www.hantek.com/en/ProductDetail_15_77.html
I'm in Canada so shipping is an issue from AESwave. I had to send my ScannerDanner book to my buddies in USA to make it more reasonable, Hantek I can get off Amazon.ca.
tiride62 wrote: Hantek one is the same, 9mm. That was a concern as well. Here's a link to the Hantek website.
www.hantek.com/en/ProductDetail_15_77.html
I'm in Canada so shipping is an issue from AESwave. I had to send my ScannerDanner book to my buddies in USA to make it more reasonable, Hantek I can get off Amazon.ca.
Ahhhh right, what a pain. But that Hantek looks good to me! I say go for it, and let us know how you like it.
Tyler wrote: Congratulations on getting your scope! Personally, I'd get a low amp probe first, and worry about the high amp probe later (or never). I've always used a low amp probe for relative compression on gasoline engines, and never had any problems. Diesel is another story, due to higher starter current draw.
I've used my Snap-On low amp clamp a few times on Diesels with no problems.
The above was taken off a Ford 6.4L with a broken exhaust rocker arm. This is how I test compression on all the Diesels I work on, I don't even own a Diesel compression tester. Just use the relative compression test.
"Silver bullets are for killing Werewolves, not fixing Cars." -Rob Longoria-
Avoid Hantek curent clamps if you can the quaily is pretty poor I have both high and low curent versions. The low current has an eye that is too small to fit over most alternator cables and the high curent clamp was delivered with a faulty switch. The tactile feel of the switches is poor and on both tools the the LED to show the unit is switched is so dim it can hardly be seen which can easily result in finding the battery dead next time you go to use it.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Last edit: 8 years 10 months ago by Andy.MacFadyen.
Andy.MacFadyen wrote: Avoid Hantek curent clamps if you can the quaily is pretty poor I have both high and low curent versions. The low current has an eye that is too small to fit over most alternator cables and the high curent clamp was delivered with a faulty switch. The tactile feel of the switches is poor and on both tools the the LED to show the unit is switched is so dim it can hardly be seen which can easily result in finding the battery dead next time you go to use it.
In North America I would probably look at what AESwave have to offer via the link on this site.
Very similar DC Amp clamps are sold under the Sealey brand in Europe I am going to order a Sealey TA311 in the near future to replace my high range Hantek.
I don't actually use the high range clamp much usually I do cranking voltage compression tests rather than current tests and I check alternator current with a Uni-T UT203 clamp multimeter. The low range amp clamp on the other hand is a very much used tool.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Last edit: 8 years 10 months ago by Andy.MacFadyen.
In North America I would probably look at what AESwave have to offer via the link on this site.
Very similar DC Amp clamps are sold under the Sealey brand in Europe I am going to order a Sealey TA311 in the near future to replace my high range Hantek.
I don't actually use the high range clamp much usually I do cranking voltage compression tests rather than current tests and I check alternator current with a Uni-T UT203 clamp multimeter. The low range amp clamp on the other hand is a very much used tool.
I'll take a look. Not the right spot to ask but maybe you can direct me to a video or post that explains the difference between voltage compression test and current compression test?
It is really simple put the scope across the battery + & - and crank the engine the peaks and troughs of the voltage trace are a inverted version of current trace.
So in voltage compression test a high voltage peak = a low compression cylinder.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
The following user(s) said Thank You: Tyler, gimmick1, tiride62
Andy.MacFadyen wrote: It is really simple put the scope across the battery + & - and crank the engine the peaks and troughs of the voltage trace are a inverted version of current trace.
So in voltage compression test a high voltage peak = a low compression cylinder.
That was a simple, easily understandable explanation, you might have a future in teaching, LOL. Thanks again; Gary
Ro-longo wrote: I've used my Snap-On low amp clamp a few times on Diesels with no problems.
Interesting. :huh: I've tried it on a Dodge 5.9L and 6.7L, ended up burying the probe, or chopping off the peaks of the waveform. Ended up falling back to a voltage compression waveform, like Andy mentioned.
Ro-longo wrote: I've used my Snap-On low amp clamp a few times on Diesels with no problems.
Interesting. :huh: I've tried it on a Dodge 5.9L and 6.7L, ended up burying the probe, or chopping off the peaks of the waveform. Ended up falling back to a voltage compression waveform, like Andy mentioned.
Now that you mention it, I don't think I have used it on a Dodge, I mainly work on Ford "Powerjokes"
"Silver bullets are for killing Werewolves, not fixing Cars." -Rob Longoria-
Ended up getting one from AESWave, an ES 695. Works fine with my DVOM but can't get a waveform to save my soul on my scope. It's most likely me but I've tried every possible combination of settings and nothing that looks even remotely like a current ramp. Scope is a Labnations Smartscope, it's not automotive friendly and I'm new to this so not a good combination. If I get a uscope any guidance on what accessory's I would want to be able to read waveforms for injectors and coils?
tiride62 wrote: Ended up getting one from AESWave, an ES 695. Works fine with my DVOM but can't get a waveform to save my soul on my scope. It's most likely me but I've tried every possible combination of settings and nothing that looks even remotely like a current ramp. Scope is a Labnations Smartscope, it's not automotive friendly and I'm new to this so not a good combination. If I get a uscope any guidance on what accessory's I would want to be able to read waveforms for injectors and coils?
Hmmmmm, I'm not familiar with that scope, but I don't see why they wouldn't work together. Maybe try measuring a steady current first, like a headlight or similar, and make sure you're getting a rational reading. I borrowed this image from Google, but it's typical of measuring bulbs:
If you do go for a uScope, you'll likely need
one of these adapters
. The master kit comes with one, the basic does not.
Topic Author
Personally, I'd get a low amp probe first, and worry about the high amp probe later (or never). I've always used a low amp probe for relative compression on gasoline engines, and never had any problems. Diesel is another story, due to higher starter current draw.
But that Hantek looks good to me! I say go for it, and let us know how you like it. 
Maybe try measuring a steady current first, like a headlight or similar, and make sure you're getting a rational reading. I borrowed this image from Google, but it's typical of measuring bulbs:
