Login bg image My IET Expand
Contact us
 
IET
Decrease font size
Increase font size
 search :  help :  home
latest topics : statistics
Topic Title: Test Equipment Accuracy
Topic Summary:
Created On: 01 June 2012 02:22 PM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
01 June 2012 02:22 PM
User is offline View Users Profile Print this message



Lorna

Posts: 2
Joined: 15 June 2009

Hello

I'm trying to understand the accuracy of a PAT tester which states the resolution, % and digit tolerances of individual test types.

My calculations are below for a hypothetical test and I would be very grateful if anyone could tell me if I'm doing right.


Resolution = 0.01 (2dp)
Accuracy = ±5% ±2 digits

Test Reading = 15.50

Step 1:
Determine the % tolerance
15.50 * 0.05 = 0.775

Step 2:
Round to 2dp = 0.78

Step 3:
Add the digit accuracy to least significant figure

= 0.78 + 0.02
=0.8

Therefore for a reading of 15.50

± 0.8 (5.16% of 15.50)

Upper limit = 16.30
Lower limit = 14.70

Thanks for your time :-)

Lorna
Top : Bottom
13 May 2013 02:29 PM
User is offline View Users Profile Print this message



kengreen

Posts: 72
Joined: 15 April 2013

Lorna,

Afraid I don't understand the Jargon in your Post - a bit before my time - but there is a sad lack of learning in the matter of estimating errors. Are you aware thjqt the first - and possibly the greatest - error lies in reading the test meter? All meters should be indicating as near as possible to their f.s.d. ?

Ken Green
Top : Bottom
13 May 2013 09:29 PM
User is offline View Users Profile Print this message



ectophile

Posts: 400
Joined: 17 September 2001

Lorna:

That working looks right to me.

Ken:

By the sound of it, that's a digital and not an analogue meter. So the concept of FSD and meter reading errors wouldn't really apply.

-------------------------
 S P Barker BSc PhD MIET
Top : Bottom
14 May 2013 06:28 AM
User is offline View Users Profile Print this message


Avatar for g3xoi.
g3xoi

Posts: 2568
Joined: 13 September 2002

Add AND SUBTRACT the 2%. because tolerances and errors are usually +/-..

Mind you, it could be worth carefully re-reading the spec because with a digital meter you should not have a reading error - it is reading 15.5 v or it is not. As ectophile says....... There is no parallax error as with an analogue meter

-------------------------
Alan

n.b. This message has a limited shelf life.
Top : Bottom
14 May 2013 09:24 AM
User is offline View Users Profile Print this message



cblackha

Posts: 48
Joined: 21 January 2003

Accuracy = ±5% ±2 digits

That might be
Accuracy = ±5% or ±2 digits - which ever is larger (rather than both).

The values you have been given are the nominal values given by the manufacturer and don't necessarily reflect the machine you have - do you have, or can you get, the calibration certificate?
Top : Bottom
14 May 2013 01:19 PM
User is offline View Users Profile Print this message



kengreen

Posts: 72
Joined: 15 April 2013

Hi to All,

I seem to have sparked quite a discussion - and who can complain about that?

It was mainly that Lorna's question reminded me of the budding amateur who settled on my visitors' stool, examined my Bench and then enquired whether he should purchase a digital or an analogue meter? My attempts to explain obviously were confusing him
and I deemed it best to let him grow a little.

Ken
Top : Bottom
IET » Electronic engineering » Test Equipment Accuracy

Topic Tools Topic Tools
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2013 FuseTalk Inc. All rights reserved.


  • Facebook icon
  • Twitter icon
  • LinkedIn icon
  • YouTube icon
Back to top
Back to top

About the IET

Sectors we focus on

Useful links



Other IET Websites

IET

© 2013 The Institution of Engineering and Technology. The Institution of Engineering and Technology is registered as a Charity in England & Wales (no 211014) and Scotland (no SC038698)