FEC200 DELVZ Test
DELVZ is a special type of VZ test that reports the differences between the VZ readings at two different test currents. DELVZ reports the sign of the difference but does not consider the sign when testing against limits.
Since the difference is expected to be small, we must tell MAXX what the maximum VZ will be so that it will use an appropriate scale. For example:
- TESTn DELVZ 100ľA 10MA 10V <100MV
MAXX will translate this to:
- TESTn DELVZ 100.0ľA 10.00MA 10.000V <.100V
If you expected some higher VZ readings, such as 25V for example, the next higher scale would have been used.
MAXX uses its calculated ramp time plus SOAK TIME for the first of the two test currents then a preset small additional time for the second current.
In the example above we would expect a positive delta (normally). However if you put the high current first, you would expect a negative delta (that's ok).
Since DELVZ measures a small change in VZ and since one of the two currents is typically small, the reading may be affected by the noisiness of some zeners at small currents.
We can't completely eliminate this problem. However, there is an option which may help a lot. You can elect (globally in CUSTOM.TXT) to have all VZ tests average several readings. Each addition reading (you select how many) takes about 1mS.
You must consider the effect throughout if you average too many readings. The first few readings averaged make the most improvement.
Note: DELTAE is an obsolete synonym for DELVZ.