These application notes illustrate the use of N4L products in solving a variety of measurement problems. For further clarity or help with any measurement issues please contact Newtons4th Ltd support: support@newtons4th.com
PSM2200 Frequency Response Analyzer
A 1 minute video sample which illustrates various display options available to a user of the
PSM1700 when in Frequency Response Analysis mode.
In this example, the PSM1700 is testing the closed
loop stability of a switched mode power supply when connected to the control loop of the supply via an
injection resistor and an N4L injection transformer.
Control loop frequency response testing
PSM units are well suited to testing transformers either manually or automatically (using a PC). Using DFT and true rms measurments over a wide frequency range, PSM units used in conjunction with our transofrer testing accessories perform most commonly required transformer tests. Testing communications transformers (PDF, 66KB)
PSM units are ideally suited to measuring the gain/phase response of a control loop by injecting a small disturbance and analysing the results. The PSM range use DFT analysis (Discrete Fourier Transform) to measure the relative gain and phase of the signal round the loop at the specific test frequency, rejecting any other frequency components present (such as noise or ripple). The test frequency can be swept automatically over the desired frequency range and the results viewed on the screen or printed out... Testing loop stability (PDF, 52KB)
LVDTs (Linear Variable Differential Transformer) consist of a transformer with one primary winding, two secondary windings and a moveable armature. With the primary energised at a suitable frequency, the magnitude and relative phase of the secondaries change as the armature is moved. This document describes how the PSM2200 QuanteQ may be used to analyse such a system. Testing LVDTs (PDF, 27KB)
FSK (frequency shift keying) is a well established technique for encoding binary data by transmitting one frequency for 'zero' and a different frequency for 'one'. It is commonly used in industrial monitoring and control systems where transmitters and receivers may be separated by long distances. In order to have confidence in the communications, it is important to verify the signal levels at the receivers to detect any degradation in performance, such as would be caused by increased cable resistance or poor connectors. Testing LVDTs (PDF, 11KB)
The PSM range are real-time analysis instruments that simultaneously acquire and process data, once the input conditions are valid. The default set up conditions for the PSM range is most suitable for measuring steady state, or slowly fluctuating signals - for rapidly fluctuating signals there are three areas where the response of the instrument can be improved using the menus or the communication commands: 1. Input ranging; 2. Filtering; 3. Frequency determination. Measuring fluctuating signals (PDF, 16KB)
Some high voltage devices have different characteristics at the lower voltages usually used to measure capacitance. The LPA400 can be used with the PSM2200 or PSM2201 to analyse devices at up to 800V pk-pk from dc to 100kHz and up to 80V pk-pk up to 1MHz. Measurements of capacitance, ac resistance, tan(θ), and even power can be made under controlled conditions that are representative of the real operating conditions for the device. High voltage capacitance measurement (PDF, 23KB)
Amongst the many measurement modes of the PSM range there is a harmonic analyzer that can measure a single harmonic or can compute total harmonic distortion (THD) from a series of harmonics. The PSM range measures THD by simultaneous computing a DFT for each of the harmonics in the series up to the maximum number specified. Measuring low THD (PDF, 23KB)
The PSM range can be used to measure the characteristics of inductors, capacitors and resistors under precise operating conditions. The two inputs are both voltage inputs so some external shunt arrangement is needed. By using an external shunt, the shunt can be optimised for the conditions of the test. The Active LCR head and Impedance Analysis Interface available as an accessory from N4L include a number of different high frequency shunts that can be selected from the instrument front panel. Alternatively, the circuit arrangements shown here can be used. LCR measurements (PDF, 90KB)