Information About Milliohmmeter
A milliohmmeter is just the tool for checking trace resistance on a printed circuit board, tracking down shorted traces, and measuring the contact resistance of a switch or connector. Its the kind of tool that would come in real handy occasionally, but not often enough to justify shelling out hundreds of dollars. Wanting one anyway, I set out to make my own. It turned out to be not only an exciting project, but a true adventure of discovery as it provided a window into the workings of lock-in amplifiers. With a lock-in amplifier topology, a microcontroller and a little firmware makes the venerable (if somewhat noisy) LM324 bipolar op-amp provide high gain and at the same time reduces noise. Improve analog performance with a microcontroller? Now THIS is a fun project! My main concern in the milliohmmeter design was how to get stable resistance readings with a suitably low test current. After all, I wanted to look at a few or few tens of milliohms, but I wanted to keep the test current low so as not to exceed the current ratings of some of the parts I want to test, and so I can run it all from a battery. For starters, 25 milliamps x 1 milliohm = 25 microvolts. This meant that I would have to be able to measure and display voltages in the range of tens of microvolts per count in a stable and repeatable manor.
Can you submit more information?
Power By How it Work
Recent Posts
-
Wetted Parts in Pressure Sensors (Diaphragm Seal, Capillary and Seal or O-ring)
Wetted parts are an important aspect to reflect on when choosing a pressure sensor. Process connecti …16th May 2022 -
Ingress Protection Vs. NEMA Enclosure Ratings
Ingress protection (IP) IP or Ingress Protection is defined as an accepted standard in the IS ( …14th May 2022 -
Melt Pressure Transmitter and High-Temperature Transmitter
Melt Pressure Transmitter A Melt pressure sensor is used to detect and control the amount of …11th May 2022