Can I use a multi-function "clamp" meter to measure resistance? [closed]

Question

Please note: Although this question mentions car maintenance, its really about how to use a clamp meter. I just happen to be wanting to use this meter to measure fuel injector resistance on my vehicle. But the question should be answerable by anyone who has experience using clamp meters to measure electrical resistance.

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Now then, this video shows a "normal" multimeter (not a clamp meter) being used to measure how many ohms of resistance their fuel injectors are providing. I'm wondering if I can do the same but with my clamp meter (Ideal 61-737):

If not, why? What is different about a clamp meter?

But if it can, then:

• Do I use the test probe leads (black and red probes that connect to the meter)?
• Do I open the "jaws" of the clamp meter and clamp them on to anything? Or do I keep the jaws closed and just use the probes the same way they are used in the video?
• The multimeter in that video shows adjusting down to 20 ohms, but my meter just has 1 resistance setting. I assume this will auto detect the range and still report the resistance accurately?

Thanks for any and all help here!

Answer 1

The "clamp" portion of the clamp meter is just for additional functionality vs. a traditional multimeter. The clamp is for measuring current and frequency only. All other functions are measured with the probes and work the same as any other multimeter (i.e. resistance, voltage, continuity, etc.)

From the introduction to the manual:

The IDEAL 61-737 Clamp Meter is an auto ranging true root mean square (TRMS) digital clamp meter that measures AC current (amps) via the clamp head, measures voltage, frequency, resistance, continuity, capacitance, diode via test-leads and measures temperature via a K-Type thermocouple, and detects the presence of voltage between 40V to 600V via a non-contact sensor in the right tip of the clamp.

For the pictured Ideal meter, you would select the multifunction setting on the dial (the one just to the left of temperature), then use the Sel & Range buttons to scroll through to resistance.

Forgot to add: The clamp also provides a handy way to hang the meter in your line of sight while you're using it for non-current functions (since both hands will likely be busy with the probes). :)

Answer 2

Your clamp meter is just an electrical multitool. The jaws are for measuring AC current only, although I think one tip also has a non-contact voltage detector.

Just use the normal test probes and the LCD display and control knob like a normal multimeter. I would expect autoranging if it doesn't have multiple Ohm range settings on the knob.

PS - Skimming through the meter's instructions before use is always a good first step :)

Answer 3

The other answers (and the manual) cover what you can/can't do. As far as why:

Resistance is measured by trying to send a small current through the item being tested. That requires electrical contact with two points on an item.

As I understand it, alternating current can be measured without direct contact because of the relationship between a changing magnetic field and a changing electric current. That is how (essentially) transformers work, which is arguably (there was a lot more to it...) the main reason why AC won the war of the currents - you can easily build transformers to convert AC between high voltage for transmission and low voltage for (relatively) safe residential use. So a clamp (or any other non-contact method) can't easily measure direct current.

It is possible to measure voltage (as with current, AC and not DC) in a non-contact method. Electric meters, beyond the basic residential models, use CTs (Current Transformers) and PTs (Potential (i.e., voltage) Transformers) to turn things like 100A @ 14,400V into 1A @ 120V, which is then measured by a meter and multiplied by the CT and PT ratios to produce the reported values. My hunch is that there just isn't that much need for clamp voltage measuring in a typical residential/small building environment because the voltages are (a) relatively safe (120V and 240V, occasionally higher but almost always well under the magical value of 600V) (b) usually no need to measure in a contact-less way. If you think you have a voltage problem (e.g., lost neutral), you just use the probes directly in receptacles or in the panel.

On the other hand, clamp current metering is very handy as it lets you test an item while it is being used - e.g., to measure the current on an active circuit or even on an entire panel (clamp around one of the feeder wires). Clamp reading, as with other types of non-contact measurement devices (e.g., a non-contact voltage tester, which this particular meter can also do using the clamp but which is typically found as a small separate tool), is safer for the user (no exposure to conductive materials), safer for the measurement tool (any current within the range of typical residential values instead of limiting to 10A) and generally avoids influencing the circuit under test.

In addition, this particular meter doesn't even have a way to measure current using the probes, and many that do (e.g., my Klein) have a relatively low limit when using the probes to measure current such as 10A - not even enough to measure a basic 15A circuit safely.