New high-speed-response type digital filter
For the WT2000 series, we installed a high performance DSP and also developed a "variable attenuation type filter method" as same as 2531 to realize multiple items simultaneous measurement and high speed response which are required for electric power measurement. This filtering method enables the attenuation constant to be varied for each sampling. Compared to the conventional analog filter it has various merits including the following: (1) it has low ripple and fast response, (2) it prevents the number of calculation processing operations of the DSP from increasing, and does not significantly reduce the sampling rate, and (3) there is no need to synchronize it with the interval of the input signal. As a result, the measurement values are unaffected even if the frequency changes or a low frequency waveform is superimposed on the input signal. This method realizes a high response of 36 items of data/250 ms.
 

Superior noise immunity
PWM type inverter equipment which is very widely used generates a voltage waveform by switching the frequency conversion circuit, hence the output contains a lot of noise. To ensure accuracy when measuring such equipment, it is important that the measuring instrument have high noise immunity. In the design of the WT2000 series, care was taken to minimize the effect of common mode noise, power line noise and pulse noise, thus ensuring highly accurate and stable measurement.
 

Integration function; High speed sampling that enables the instrument to measure abrupt changes of input value.
The integration method used in the WT2000 series enables the instrument to continuously acquire data by sampling the input signal at a high rate of about 110 kHz. As a result, the instrument can measure abrupt changes in input value, which was difficult to realize with conventional measuring instruments, thus enabling integrated values to be measured with very little loss of data. (There is virtually no delay or pause period due to the response of the filter.) With YOKOGAWA's conventional models, the resolution of the displayed value resulting from an integration operation is fixed by the maximum integration time, hence for short period integration, the bottom digit was not displayed and the resolution was insufficient. The WT 2000 series uses an "auto resolution method" in which the display resolution automatically changes along with the lapse of the integration time, ensuring the maximum resolution even for short period measurement.