Klein CL120 tester with amp clamp with bogus readings

Status
Not open for further replies.
jaylectricity

jaylectricity

Senior Member
Location
Massachusetts
Occupation
licensed journeyman electrician
Hello...the short version:

I have the Klein CL120 and I'm getting bogus readings. I used the plug adapter so I could plug into the receptacle, then plug the equipment into the adapter and get the reading from that. I'm regularly getting readings of 50-100 amps on a 15 or 20 amp circuit. Is there something that causes this? It's frustrating because it's no help at all when diagnosing problems.

More details:

I was getting that kind of reading on a dishwasher. I assumed that maybe my tester was a little beat up and not working properly. So I bought a second one that I don't use much, keep it protected in a box in the cab of my van.

Our power went out during the storm in New England this week. So I have a brand new Generac GP2200i and I run an extension cord into the house where I split it to run to two refrigerators, the gas-fired forced hot air furnace and our entertainment center. I know it's close to the limit. One of the fridges is new and draws maybe 3.1 amps. The other fridge is old and is more like 7 amps. The furnace I was unsure of and the internet and TV are maybe 2 amps. The generator is 1700W (with 2200 available for startups).

So before the splitter I put the brand new plug adapter into the cord coming from the generator. I put the amp clamp on it and watch. Everything starts out normally. I plug one fridge in, it's 3 amps, the other fridge it jumps to about 9. Stays there for a bit as the heater is starting up, but no fan motor yet. Fan motor kicks in and the meter reads 13 amps. Jumps to 15, then back down. All of the sudden I get "OL" for overload. I have it on the 20A range. So I switch it to the 200A range and it reads 50 amps and then eventually 90. It stays like that and I never see it go lower than 88A. Ten minutes go by. I take the clamp off. I turn it off and on. I put the clamp back on...still way up there. I alternate between the grounded conductor and the ungrounded conductor. Still the same.

Let's assume the reading was correct. No way this generator keeps running with that kind of load. And previously when I had it on a 20A circuit for a dishwasher, no way the breaker doesn't trip with 10 minutes of 90A running through it.

Is there something I'm missing? Are these testers just garbage? Anybody else experience this?

End long version

I know it's late, but I just got a chance to sit at the computer. I'll check the thread a little tonight if there are any questions, but most likely I check back in either before work or at lunch.

Thank you.
 
jaylectricity said:
I have the Klein CL120 and I'm getting bogus readings. I used the plug adapter so I could plug into the receptacle, then plug the equipment into the adapter and get the reading from that. I'm regularly getting readings of 50-100 amps on a 15 or 20 amp circuit. Is there something that causes this? It's frustrating because it's no help at all when diagnosing problems.
Click to expand...

The plug-in adapter that comes in the kit with the CL120 appears to be the 69409 which is a 10X version. So it has ten turns inside of it which multiplies the magnetic field and therefore fools the meter into thinking the current is 10X higher. But it gives you higher resolution as long as you don't overload it, which you were doing with some of your measurements. You can overload the meter in the 200A mode if you put more than 20A through the adapter.
Also, you have to divide the reading by 10 to get a correct value.
 
Last edited:
synchro said:
The plug-in adapter that comes in the kit with the CL120 appears to be the 69409 which is a 10X version. So it has ten turns inside of it which multiplies the magnetic field and therefore fools the meter into thinking the current is 10X higher. But it gives you higher resolution as long as you don't overload it, which you were doing with some of your measurements. You can overload the meter in the 200A mode if you put more than 20A thought the adapter.
Also, you have to divide the reading by 10 to get a correct value.
Click to expand...

That's helpful. I'm going to try that with a few expirements. Seems silly that it isn't worked into the equation with the meter.

pjones said:
I don’t see anywhere in the product listing that says it is true RMS. I’m guessing the combination of a generator and the lack of True RMS is causing your issues.
Click to expand...

That doesn't explain the same phenomenon when I put it on a dishwasher running from the POCO service.
 
It's interesting that this kind of 10X adapter where you can clamp around either side of it must be built with 5 turns on the neutral wire and 5 turns on the hot wire. But one of the wires would need to be wound clockwise and the other counter-clockwise so that their magnetic fields add since their currents flow in opposite directions.
I hadn't given this any thought before this, and so thanks for the post.
 
211028-2400 EDT

jaylectricity:

You need to figure out how to answer some of your own questions.

Starting point:

1. Measure you power company voltage at some known good 120 V outlet. This will provide an estimate that your basic meter function is working correctly. Current measurements are generally a voltage measurement in the meter from an internal shunt resistor..

2. Next without using a current probe put your meter in current mode in series with a 100 W 120 V bulb connected to your power company 120 V source. The approximate reading should be about 100/120 = 0.83 A. Repeat using your current probe around one wire to said 100 W bulb.

3. Next do the measurement using the splitter adapter and the meter probe. Any of your current measurements should be about the same.

4. Next put a 120 V 1500 W space heater as the only load on the splitter device. What is the reading? Should be abut 12.5 A.

All of these tests will give you some idea of how your measurement systems function.

Report back.

.
 
gar said:
211028-2400 EDT

jaylectricity:

You need to figure out how to answer some of your own questions.

Starting point:

1. Measure you power company voltage at some known good 120 V outlet. This will provide an estimate that your basic meter function is working correctly. Current measurements are generally a voltage measurement in the meter from an internal shunt resistor..

2. Next without using a current probe put your meter in current mode in series with a 100 W 120 V bulb connected to your power company 120 V source. The approximate reading should be about 100/120 = 0.83 A. Repeat using your current probe around one wire to said 100 W bulb.

3. Next do the measurement using the splitter adapter and the meter probe. Any of your current measurements should be about the same.

4. Next put a 120 V 1500 W space heater as the only load on the splitter device. What is the reading? Should be abut 12.5 A.

All of these tests will give you some idea of how your measurement systems function.

Report back.

.
Click to expand...

Your condescending tone aside, all of those measurements would seem normal, but what has happened is the reading on the space heater would be nearly 100A. That's why I'm trying to figure out the deal with the amp probe function and it's completely wacky readings.
 
211029-1713 EDT

jaylectricity:

Create a short cord with all wires exposed, not in a cable, so you can clamp around one current carrying conductor. Use this adapter to measure your heater current. A heater is a resistive load. Power company voltage is usually quite clean. Just a little distortion near the peak from all the capacitor input power supplies on the power grid. Whether you use an average reading AC meter or a so called true RMS meter should make no appreciable difference.

What are the results?

.

.
 
211029-2103 EDT

With either my Fluke 27 or 87 I can not get a useful reading of the starting current of a 1/3 HP induction motor. The start winding of this unloaded motor is only closed for about 100 mS. The peak amplitude of the starting current is about 80 A and RMS about 56 A.

Both meters MAX readings are below 10 A. My scope and the meter are in parallel across the output of a Fluke Hall device current probe on its 200 A range.

Thus, neither Fluke meter is useful to measure starting current of a motor that starts quickly, nor the inrush current to a transformer or incandescent bulb. The transformer and incandescent are both about a 1/2 cycle events (8 mS).

If I want to study short time events I will use a scope.

My Fluke 27 reads 122.4 V when in parallel with my Fluke 87 the 87 reads 122.7 V at my bench.

.
 
Status
Not open for further replies.
Top