1. i am building a current sensing circuit. currents range from 1-6amp and the sense resistor is this funny looking "air" 0.05ohm resistor (looks like a piece of flat wire bent into a flatened letter C, is meant to be lifted off the board so it can cool better in the air). i'll be using a op-amp with gain of 20 to monitor the voltage across the resistor. the output of the op-amp is then trimmed and fed to a lm3914. the monitoring circuitry is to be built on a daughter card for modular design purposes and will be connected to main board via some mezzanine headers (like those you see for IDE cables in a PC, but these are for board-to-board applications). i am concerned about the DC insertion losses found in the two headers connecting to each other from main board to daughter card. i can compensate for these losses via output trim on the op-amp but the concern there is that the insertion losses will vary over time due to metal corrosion of the header pins, heat, and vibrations. i can opt to put the op-amp IC on the main board but that means if the daughter card is not being used i have circuitry on the main board being powered but not being used. any suggestions?
2. can anyone suggest a PC board maker that can make 2-4 boards for prototyping purposes. i use DipTrace to output gerber files and drill schedules, just need to find a place that can run a few boards without my wallet going into the IOU state....... any suggestions?
2. can anyone suggest a PC board maker that can make 2-4 boards for prototyping purposes. i use DipTrace to output gerber files and drill schedules, just need to find a place that can run a few boards without my wallet going into the IOU state....... any suggestions?