Digital display plug-in

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT FIG.
1 shows a block diagram of the digital display module 10 (area within dashed lines) connected to any metering device having a recorder output 12, range switch 16 and function switch 18.
The recorder output 12 exhibits excellent linearity and is attenuated enroute to a digital panel meter (DPM) 26 by means of a voltage divider 14 such that the number 1,000 displayed on the DPM 26 corresponds to a full scale deflection of the analog meter in the measuring device.
A "probe" switch 20 on the front panel of the module encodes the logarithm of the scale factor associated with the particular probe in use to a two's complement binary number, with the full scale range information from the "range" switch 16 and the "function" switch 18 being encoded in a similar manner.
It should be noted that the probe switch 20 is needed due to the different scale factors of the many probes which are in use.
If only one probe is to be used, this switch 20 is unnecessary and the proper scale factor can be permanently wired into the circuit.
The encoded information from the switches 16, 18 and 20 is processed by a scale computation circuit 22, which is connected to decimal point switching circuit 24 for correctly positioning the decimal point.
This is quite important since the range information is automatically included on the display, necessitating an accurate representation of the correct decimal point location.
The scale computation circuit 22 is also connected to a message display unit 30 through display switching circuit 28 for selecting the correct units of measurement.
The logarithmic coding of the switch positions reduces scale computation to simple binary addition, eliminating the need for electronic multipliers (See FIG.
2).
Resolution and accuracy of the digital panel meter 26 are such that full system accuracy is maintained using the .
times.
10 scales of the range switch only.
Therefore, to allow simplification of the circuitry, the module enters a standby mode on any