Which one is right?

[MarkyMarkNC]

If you have a Fluke meter, there is often a guy at trade shows or supplier open houses from Fluke that will calibrate your meter for free.

 

[zog]

How do you find them?


As in, send it in to Fluke?

How much does this cost?

I have used these guys at every place I have worked (Besides one), dont know how much it costs to send something in, maybe $20 or so, they come to our shop and calibrate everything, charge us by the day.

http://www.etiinc.com/index.html

 

[zog]

If you have a Fluke meter, there is often a guy at trade shows or supplier open houses from Fluke that will calibrate your meter for free.

You get what you pay for, the calibrations needs to be doen using calibrated instruments traceable to the National Institute of Science and Technology (NIST), you need the proper documentation for this to meet any requirement for you meter cal program.

But if you just want to know if your meter is working right I suppose that would be an option. He is just comparing it to a meter he has there. Think he might say your meter is not accurate and you should buy a new Fluke?

 

[iaov]

The difference in readings may be that one meter is a true RMS meter while the other is not.

 

[chris kennedy]

The difference in readings may be that one meter is a true RMS meter while the other is not.

George, look just above both screens in the picture, post 1.

 

[active1]

Here is information about Flukes services. It says they do other brands. I have not used them myself.

http://us.fluke.com/usen/Service/calservice/default.htm

 

[iaov]

I Seee says the blind man!!

 

[MarkyMarkNC]

You get what you pay for, the calibrations needs to be doen using calibrated instruments traceable to the National Institute of Science and Technology (NIST), you need the proper documentation for this to meet any requirement for you meter cal program.

But if you just want to know if your meter is working right I suppose that would be an option. He is just comparing it to a meter he has there. Think he might say your meter is not accurate and you should buy a new Fluke?

Hmmm...It probably wasn't an ISO 9001 calibration, but I'm pretty sure they were promoting it as an official calibration. I don't remember what all they did, but it was a lot more involved than comparing to another meter. They took down each meters serial number, and entered them online when they were done.

 

[brian john]

How? Where? I've never had a meter calibrated. Inquiring minds want to know!

All my meters are calibrated, once a year a company that specializes in calibrating spends 2 days at my office calibrating all my test equipment.

 

[steelersman]

How do you find them?


As in, send it in to Fluke?

How much does this cost?

a few years back i sent in a fluke to be calibrated. I had to send it to Washington state and it cost me somewhere around $70 total.

 

[infinity]

The difference in readings may be that one meter is a true RMS meter while the other is not.

Look again, they both are. :wink:

 

[Goroon]

Whats the "APO" on the Ideal meter display indicate?
I see TRMS on the Greenlee

I dont have any of those Radio Shack meters.

 

[Pierre C Belarge]

1. check the prods as they are positioned in the receptacle swipe(s). Is one receptacle tighter than the other, etc...

2. check the leads of the different testers.

3. You have mentioned the testers are a little older, one used less than the other. Where are these meters stored?

4. have you tested the same testers to another load?


A very good thread and interesting to see if the result of the readings is found.

 

[don_resqcapt19]

They may both be right. There may be a less than perfect connection with one of the meter leads ( resistance caused by arcing or corrosion ).

Given the high input resistance of these meters it is not likely that a poor connection would change the reading. The only way resistance changes the voltage is the result of the voltage drop that is created by the current flow through the resistance. The current draw of these meters is much too low to cause a voltage drop that is measurable with these meters.

 

[zog]

Hmmm...It probably wasn't an ISO 9001 calibration, but I'm pretty sure they were promoting it as an official calibration. I don't remember what all they did, but it was a lot more involved than comparing to another meter. They took down each meters serial number, and entered them online when they were done.

I will stop by the Fluke booth at Powertest in March and see what they are doing with this, might bring a few meters with me too

 

[chris kennedy]

Whats the "APO" on the Ideal meter display indicate?
I see TRMS on the Greenlee

Auto Power Off

I dont have any of those Radio Shack meters.

Great, neither do I.

1. check the prods as they are positioned in the receptacle swipe(s). Is one receptacle tighter than the other, etc...

2. check the leads of the different testers.

3. You have mentioned the testers are a little older, one used less than the other. Where are these meters stored?

4. have you tested the same testers to another load?


A very good thread and interesting to see if the result of the readings is found.

1. All good

2. All good

3. The Greenlee bangs around the job sites with us, the Ideal stays in my briefcase.

4. Yes, first noticed the problem at work.

 

[Pierre C Belarge]

If you are saying by your answer to #4, that this is common for the meters at other locations, I would say one of if not both meters are not functioning properly.


Like you mentioned earlier, that you usually do not have meters very long, maybe it is time for a new meter...or two.

 

[chris kennedy]

If you are saying by your answer to #4, that this is common for the meters at other locations, I would say one of if not both meters are not functioning properly.


Like you mentioned earlier, that you usually do not have meters very long, maybe it is time for a new meter...or two.

Don't think for a second thats not going through my mind.:smile: I have around $400 in those two. I'm not knockin Ideal here but I think I payed around $280 for that and the Greenlee does the same thing for $150.

If I find that it will be $80 to $100 to calibrate both, I see a new DMM in my future.

 

[gar]

090215-1431 EST

Do not get too hung up on a true RMS vs an average reading calibrated in RMS for a sine wave. If you have an approximately good sine wave, then the readings will be close.

The Vrms value of a sine wave is 0.707 of the peak. The Vave of a sine wave is 0.636 of the peak. Thus, a DC meter with an applied full wave rectified sine wave will read 63.6 V for a sine wave of 100 V peak. An RMS meter will read 70.7 V. To make the DC meter read 70.7 V you redraw the scale, or you change the series calibration resistor from 100,000 ohms for reading DC with a full scale of 100 V to 100,000*0.636/0.707 = 89,958 ohms to make it read the RMS value. This would be for a 1 MA meter movement.

A full wave rectified balanced square wave has an average value equal to its peak. Thus, the reading on the AC average reading meter calibrated for RMS of a sine wave will read Vpeak*0.707/0.636 = 1.11*Vpeak or in the case of the 100 V peak it will read 111 V. The true RMS meter will read 100 V because this is fundamentally no different than if it was reading a steady 100 V DC input.

Going in a different direction and making a short pulse produces a greater disparity between the two types of meter.

For a lot of common non-industrial, non-inductive current loads there will be negligible difference in the readings between an average reading and true RMS meter.

I have various VOM meters dating from 1947 that have never been calibrated and read close to one another. On my line voltage a Simpson 270 from 1975 reads 125 V, a Fluke 27 (probably over 10 years old) reads 123.4 V, a cheap RV plugin meter with expanded scale reads 122, a Beckman 4410 (older than Fluke) reads 123.3. Note: the Simpson is at half scale for this reading, and the Simpson and Fluke are within 1/2% at 10 VDC which is full scale on the Simpson.

For general electrical use I would think that you could check your meter(s) against several quality instruments that your buddies have to determine whether any need recalibration. Then only send in units that need recalibration. On receiving recalibrated units you could use these for your reference to recheck others. The Fluke specification on my 27 is +/-0.1%+1 count on the DC voltage ranges. Not quite as good on AC and then it is frequency dependent.

You could create a DC calibration source with a 1.5, 6, or 12 V dry cell battery. If you want to set a specific voltage, then added a potentiometer. Connect both your reference meter and the meter under test at the same time to the pot. Adjust the pot for a desired voltage on the reference meter, then read the meter under test.

Divider resistors or the equivalent are used for scaling. For example with the Simpson 270 if I check the 50 micro scale at full scale and it is 50 microamps, then all DC readings at full scale will be within some resistance tolerance of the correct value. 50 microamps corresponds to 20,000 ohms per volt of series resistance. Resistors used in good meters are very stable and unless damaged can be assumed as probably good to their tolerance level. Rough checks on various ranges will probably give you a good estimate if the resistors are good.

chris:

Try as many meters as you have on a simple DC source and compare their readings. If DC seems good, then do the same on AC.

.

 

[chris kennedy]

chris:

Try as many meters as you have on a simple DC source and compare their readings. If DC seems good, then do the same on AC.

.

Just tested both on a spankin new 9V battery. Got 9.3V on the Greenlee and 9.26 on the Ideal. Of course you have seen the AC results.