Automated Measurements: Capacitor ESR

Automating complex measurements is hard.  Automating simple measurements is hard too.  To automate instrument settings, data acquisition, plotting, measurement calculations requires a good understanding of things like:

• USB, TCP/IP, or serial interface access
• Instrument driver settings 
• SCPI/IVI 
• Labview, C+, Python or some other language

   
We think intelligent use of cloud computing can transform how this is done and measuring capacitor ESR is a good example.

In ideal settings, capacitors can be assumed to only have capacitance.  Realistically, there is some finite level of resistance that is seen in series with the capacitor, this is called Equivalent Series Resistance (ESR).  Over time, the capacitor's physical properties degrade and the ESR goes up.  In worst case scenarios the ESR is large enough that the capacitor fails and does damage to the other components.   To measure the ESR an engineer has two main options:

1)  Buy a purpose built ESR meter.  They are cheap, but can't do much else.
2)  Use the scope and function generator already on your work bench.  

If you pursue option 2, you still need to do the following:

• attach the probe leads
• configure the scope
• configure the function generator
• jot down the measurements
• perform calculations to get the ESR

With GradientOne it is as simple as attaching the probe leads, select the measurement cap_esr, then hit 'go' and you have your result.

In this example a user selects the Tektronix MDO3012, which has an integrated function generator with its oscilloscope.

The function generator is issuing a square wave at 1 Vpp, 220 kHz.  The scope captures the signal, transmits the settings and waveform to the cloud, where GradientOne algorithms calculate the voltage drop across the capacitor.

The data collected by the GradientOne algorithm is then plugged into the formula:

The results of the measurement, the trace, and the data, are stored in an automatically generated report that is stored on the server.  You can also upload your images associated with your test, store them on the server, and the report generator includes them.

Our vision is to continue to expand our measurement library and to allow customers to upload their own, share them inside or outside their organization.