Most electrical product testing is to a published standard, but not always.  MET Labs has a rich history of developing custom test plans that meet manufacturers’ specific needs. 

One reason for developing a custom test plan is to check equipment performance against marketing claims made by the equipment manufacturer, or to check the performance of your product against a competitor’s product.  Performance can include reliability, accuracy, safety, energy efficiency, or other factors.

A recent customer example comes from a large industrial solutions company that asked MET to test the performance of its noise isolation transformer against its own marketing claims.  The transformers are sold to schools, hospitals and small offices (especially in high lightning strike areas) to protect against transient overvoltage, spikes/surges and other undesirable noise.

The company asked us to measure the capacitance and the common and normal mode noise attenuation between the primary and secondary of their transformers.  We found that there was no established test procedure standard to refer to, so we developed one and had it approved by the customer.

Here is the basic setup we developed to measure the transformer’s capacitance: The transformer and test equipment was wired according to the accompanying diagram.  At each test frequency, the signal generator was set to output Vrms (Vin), and the spectrum analyzer was set to measure Vrms (Vout).  The following formula was used to calculate the capacitance:

C = [Kf((Vin/Vout)-1]^-1, where K=2π*50Ω and f=frequency in Hz. 

The accuracy of this test method and our test equipment was checked by measuring a range of known capacitors prior to measuring the transformers under test.

Similarly, we developed test methods to measure common and normal mode noise attenuation.

What were the results?  Customer test results are confidential so we can’t say, but the customer is satisfied and we are looking forward to the next non-‘standard’ testing challenge they have for us.

Have a challenging application?  Tell us about it – we can help.

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