Low drift analogue precision current source. High vibration withstand achieved with mechanical restraint using flexible moisture resistant polymer. Extremely high temperature stability and low lifetime drift achieved with careful circuit design and component choice.
Precision Isolated Low Drift Current Source
Driving PT100 temperature sensors requires an accurate, noise immune and robust source. Environments where PT100s are used for monitoring are often electrical noisy and can have issues such as earth currents and common mode noise.In order to avoid these problems ELMG designed, developed and built an isolated precision low drift current source with very low drift. The total observed drift for the 2.5mA source after operating for two years is less than 0.0001 mA.
Measuring the loop transfer function allows the stability and robustness of the of the power converter control to be designed.
Control Loop Stability
Control loop stability measurement of power converters means the closed loop feedback system can be designed to be stable and robust to power converter variation.ELMG control loop design expertise includes loop stability for digital and analogue control. Specialties include linearisation of converters and parallel connected converters.
Distribution of the filter gain for the expected component variation.
Probability that the 50Hz gain for the filter is less than
Effect of component variation on ripple filter performance
Ripple control provides the ability to manage load via the AC network itself. Signalling travels down the AC line to the ripple controlled equipment which is switched on or off.Extraction of ripple control signals from the mains voltage waveform involves separating the fundamental frequency from the ripple frequency. The analogue filter to separate the AC fundamental from the ripple can use relatively low precision components to keep the cost as low. This is possible if in the variation was small enough across the three hundred thousand units.
To ensure that the requirement for attenuation of 20dB was met the effect of the component value variation on the filter performance is found. The predicted statistical variation in the fundamental frequency gain showed that a -20dB gain or smaller was achieved in 99.7% of the units built. This means the low cost filter option could be used with cost saving of eight dollars per unit.
