Hello Tobias, nice project! I would very much like to see how this evolves.
But just one thing: You mention you measure voltage before and after the shunt to get a current reading. This sounds to me like you are wasting a lot (!) of ADC resolution for that fact because you would always subtract two voltages who are roughly of the same magnitude.
Ever thought about an instrument amplifier (very sensitive differential amplifier) across the shunt? You could also use some current sense ICs who have all of these included (Linear Technologies has a lot of them).
Jens
Hello, I am new to this group and I would like to introduce myself with a project that I have been working on. This is my attempt to create a DMM using IN-12s, a IN-15A and a IN-15B as display. I used my nixie clock board as base, so it can double as a clock when not used as multimeter =) http://tobiasmugge.files.wordpress.com/2012/05/dscn4039.jpg http://tobiasmugge.files.wordpress.com/2012/05/dscn4034.jpg The uC is a Atmel Atmega328p. I downloaded arduino bootloader on it. I am using supertex HV5522 as drivers for the nixies. Two of them for 64bits. A friend of mine wrote a library for it that includes brightness control via the HV5522 blank pin. He is currently programming the clock while I work on the DMM. Power consumption is around 3W. DC power supply from 9 to 12V. The voltage for the tubes is boosted from the input voltage using a switch- mode power supply based on the TubeHobby one. The pictures and video shows voltage reading: is the only measurement I implemented on the software so far. Still thinking how to approach the scales/units. I have a shunt resistor on the board and I plan on having voltage, current, power, frequency and duty cycle for DC. I am using a I2C A/D with a PGA, measuring voltage on both sides of the shunt. This was a fairly cheap solution, but the way I did it only works for DC and the range is 0 to 32V. But allows me to measure current and voltage at the same time =) I have a video of the thing working: http://www.youtube.com/watch?v=PNYnFTeADow The maximum error I measured was 1,2% when comparing to my not-that- bad-multimeter. I plan on implementing resistance, capacitance, inductance and AC voltage/current capabilities. Suggestions will be greatly appreciated! The IN-15A showed on the pictures is not fully lightened. I am following Nick suggestion to burn it at 6mA for one hour. So far so good. I am still trying to find some IN-12B as those include the dot. I do have 4 bits free on the HV5522 that I could use to drive IN-12B dots or INS-1.
-- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
