The WD7 and WD6 cards are resistor decades, which can be programed freely from 1 ohm to 1.048 megohm in 1 ohm steps. The programed value has a tolerance of 0.1%. The max. power consumption is 0.6W. The resistors are load trimmed and have an extreme low temperature coefficient. Because of a special interconnection on the card, we were able to compensate for the transition resistance of the relay switches. So the overall accuracy has been significantly increased. As a result, the specified tolerance refers now to the complete resistance range.
The WD7 card has all functions of the WD6 card, but in addition the possibility to program a second resistor like the one above, or a potentiometer with both resistors combined.
The card must be re-calibrated every 12 months at our calibration lab.