Mr. Robinson,

Nothing said necessarily represents the opinions or policies of my employer(s).

Agree with Doug Powell's comments.

Methinks this is a bit more of an internal policy for the NCB/NRTL than what 
has been specified by regulation or standards.  The conformity assessment 
bodies where my employers have been subject to an 'agency client data' program 
all have evaluated the company lab's test equipment, associated calibration 
program, and the lab's measurement uncertainty calculations. All of my lab 
accreditations indicated each particular test where data can be accepted, 
described the authorized test equipment, and listed the authorized signatories 
for the TRF; but only three of the five accreditations of my employers' labs 
indicated the uncertainty for each type of measurement.

Some NRTLs do measurement uncertainty via an "Calibration Certificate 
Analysis", where the calibration people must provide uncertainty on  the issued 
cal cert.

Repeatability of component temperature measurements for power supplies, is 
difficult and can be problematic, and is oft done poorly by the NRTL. Few 
technicians understand the physics of the Seebeck effect, and fewer understand 
component performance and function for modern power conversion equipment that 
would affect thermocouple performance. During previous 18 to 20 years, have 
seen only two particular instances of an NRTL lab doing the heating test where 
the data was both repeatable (error band coincident with uncertainty) and the 
test conditions were correct (this is out of over 20 visits to various labs on 
behalf of clients).


From: Kevin Robinson [] 
Sent: Tuesday, September 20, 2016 6:59 AM
Subject: [PSES] Measurement Accuracy

I was wondering if anyone was aware of any guidance documents that provided 
acceptable levels of uncertainty when conducting various tests.  The specific 
measurement that I am interested in this case is temperature measurements, but 
I would be interested in seeing other guidance for other measurements as well 
(voltage, current, force etc.)

I know the IECEE has published a CTL decision sheet on equipment accuracy, but 
I was wondering if there was other industry guidance available.

I have a situation where a product was subjected to a temperature test three 
times by three different individuals using the same test equipment, and the 
delta in some instances was nearly 12 degrees C (53.3 - 64.8) for the same 
component.  Just looking for some additional guidance documents or standards 
that would help me convince the powers that be that such errors are 

Kevin Robinson

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