Any interest in a multimeter to SD data logging program?
I have been playing with a cheap, $30, multimeter with an RS232 interface. It even includes a k type thermocouple.
The included PC software did not function with my Win7 machine so I decided to try building an Arduino SD logger.
I found the meter's serial protocol http://www.multimeterwarehouse.com/TP4000ZC/TP4000ZC_serial_protocol.pdf.
I discovered that the RS232 cable is just two wires connected to an opto-isolator. I built a simple cable for the Arduino using a 10k resistor and a 3.5mm stereo plug.
I am able to read the meter's serial data using the Software Serial library and decode the data using the above specification for the meter chip.
Here are some sample records from a debug session.
24 -006.4 m V 35 01.17 n F 66 032.8 C 72 -001.3 u A 157 120.9 V AC 211 40.84 Hz 364 354.6 k Ohms 366 1.460 M Ohms
The first number is the time in seconds, the second number is the value on the meter's display.
The third column is the multiplier (n = 1e-9, u = 1e-6, m = 1e-3, blank = 1, k = 1e3, M = 1e6).
The fourth column is the unit (F = farad, C = degrees Celsius, A = amps, V = volts, Hz, or Ohms).
The fifth column contains AC or is blank.
I plan to write CSV files and write the multiplier as a number.
Several other meters use this chip.