Calibration of Digital Panel Meters

[mooi mooi]

Hi ,
Can anyone out there advise me on this issue.
We are measuring the input voltage,current,wattage and power factor with the use of 4 digital panel meters that has got no adjustment watsoever.
We read and record the values for quality jugdgement purposes. Since there is no way for us to do calibration for these meters, we verify the voltmeter and ammeter against a calibrated voltmeter and ammeter at the start of every shift to ascertain that they are reading the same ( within the acceptable tolerance limit). Or maybe we do it once a month or so to verify its accuracy. Is this method acceptable? Or do we need to send these meters for calibration with an outside agency?.
Your inputs please.
Thanks

 

[Marc]

What are these used on? Are you referring to panel meters on process equipment?

 

[somashekar]

Hi ,
Can anyone out there advise me on this issue. <snip>

Digital panel meters are factory calibrated using a calibrated source and calibration software. The basic measurement that you can calibrate yourself as you have detailed (voltage / current / frequency) should be fine.
Other power and energy outputs are derivatives from the basic measurement which the DPM software, embedded in the meter processor will perform and display suitably.
Any outside agency cannot do much, unless you send back to the factory for them to re-calibrate using the source and software that is propitiatory with them.
Note: I understand that you are referring to DPM's in DIN 96 x 96 mm or 96 x 48 mm cutout sizes in panels.

 

[mooi mooi]

Thanks ..for the reply.
I think i'll just do as what i said earlier.
Was also wondering how could they calibrate tons of dpms in big refineries or process that have control rooms with plenty of such devices. I gues the quick and easy way would be just to verify them with calibrated measureing devices.
mooimooi

 

[Big Jim]

Thanks ..for the reply.
I think i'll just do as what i said earlier.
Was also wondering how could they calibrate tons of dpms in big refineries or process that have control rooms with plenty of such devices. I gues the quick and easy way would be just to verify them with calibrated measureing devices.
mooimooi

Verification is calibration activity.

"When necessary to ensure valid results, calibration equipment shall be calibrated or verified, or both . . . "

And don't forget the beginning of that sentence "When necessary to ensure valid results . . . ". If it isn't necessary for valid results it doesn't need to be calibrated.