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3-1/2 Digit DPM ICL7107 Digital Panel Meter


This is a Digital Panel Meter based on ICL7107.  This was the workhorse Digital Readout chip before Low power uC designs were developed. Even now it is the easiest way an analog parameter can be displayed in an instrument.

3-1/2 Display is just enough resolution for recording process data or troubleshooting equipment. With 4-1/2 you notice the problems of thermoelectric EMF of probes and connectors. That is one reason gold plating is used another being low contact resistance. In 4 1/2 the reading can change due to contact resistance too, if the input impedance of the analog signal conditioning is low or the protection diodes, RC filter caps are leaky.

DPM ICL7107 Digital Panel Meter

The basic application Note is from Intersil - ICL7107 Device Information. When you measure an analog parameter from a sensor; you attenuate or amplify it, to scale to the A/D converter range. You also need to protect or isolate the analog front end from high energy mis-connections, which will happen during field use. The operator should not get injured from any high energy leakage while measuring.

DPM ICL7107


Resolution is the finest detail you can enumerate in a parameter or object. You can say the crowd was 3000 or 4000 people. Here 1000 is the resolution, finer data does not matter here. You would also hear things like, there were  80 to 90  boys in that  classroom. 10 is the  resolution there.

Accuracy is how precise a statement or number is. If there was 85 boys in that class, the above statement is accurate. If there was 65 boys, the measuring method or process needs calibration or examination.

PNG-Schematic,     PDF-Circuit,    PCB - DT  L1 SS  SM
3-1/2 Digit DPM ICL7107 Digital Panel Meter - del30002

The PNGs of PCB is 600dpi 16 color. It is to be scaled appropriately. The part numbers on circuit may not match the Silk Screen.

In this circuit, the plastic caps should be of very low leakage. Multilayer plastic caps are good for instrumentation.