Posts tagged ‘Measurement’

When to Use An Electrometer?

Electrometer is a piece of highly specialized electronic test equipment. Most of us would naturally associate it with low-level measurements (e.g. low current pA, fA and high resistance GΩ measurements) only, but the situations under which you might need to use an electrometer are actually far more common then you might have thought. In this post I will discuss a couple of situations where using an electrometer is crucial. And at the end of the post I included a video for some demonstrations. Continue reading ‘When to Use An Electrometer?’ »

Thermistor Parameter Measurement — II

Last time I showed a simple circuit that can be used to measure unknown thermistor parameters. The circuit is basically just a power MOSFET using a voltage and duty cycle controlled PWM signal to drive the gate and thus generates a temperature reference which is measured by both the unknown thermistor and the precision temperature sensor LM335. By measuring the voltage drop across the thermistor at different temperatures, we can obtain the R-T curve of the thermistor and thus estimate the parameters that define the R-T curve using some known models. Continue reading ‘Thermistor Parameter Measurement — II’ »

Thermistor Parameter Measurement — I

Over the years, I have gathered quite a few NTC and PTC thermistors. But most of them are unmarked so it would be difficult to use them in an accurate way without knowing the parameters. So I decided to build a simple circuit that can be used to trace the temperature-resistance curve, and the parameters can then be estimated using the measured data points. Continue reading ‘Thermistor Parameter Measurement — I’ »

On RMS Voltage Measurement

Just because you are using a true RMS multimeter does not automatically mean you should always trust the readings of your measurements. In fact, most true RMS multimeters can only offer reliable readings under certain conditions. In this post, I will examine some of the pitfalls in RMS voltage measurements and show you some concrete examples on how RMS readings can sometimes be misleading. Continue reading ‘On RMS Voltage Measurement’ »