tohmm TOH Multimeter
 

https://pbs.twimg.com/media/BkusonRCAAA4BcG.png
Multimeter

Icon by solbrit

Re: tohmm TOH Multimeter
 

New TOH idea by bill_klpd, Multimeter TOH.

Seems that i started to think about this further.

First, sketching the UI:
https://lh6.googleusercontent.com/-0...0409100124.jpg

Block diagram of the electronics part: (First draft)
https://lh5.googleusercontent.com/-v...o/tohmm100.png

First 3D sketch:
https://lh4.googleusercontent.com/-L...m-mockup-1.png

HW Specs:

• Voltage measurement ranges 200mV, 2V, 20V, 200V DC (AC TBD)
• Current measurement 200mA, 2A (TBD)
• Resistance measurement 200, 2k, 200k, 20MEGohms (TBD)
• Possibility to measure low-side current and high-side voltage at the same time --> Power (W) measurement.
• Isolated from phone (floating) should be safe to keep USB charger connected while taking measurements.
• Fused current measurement

SW Specs:

• Continuous measurements with adjustable rate
• Min/avg/max display
• Single shot measurement when in hold mode
• Beep when new min max value, or beep when short in Resistance mode.
• Logging of readings with timestamps
• Trigger events with alerts also possible TBD
• "Plotter" view on separate page of latest results TBD
• or simpler graph view in main page TBD

Re: tohmm TOH Multimeter
 

future is coming!

also please add short circuit mode checking with beep signal.

Re: tohmm TOH Multimeter
 

Hmmh, why not an oscilloscope, or at least a possibility to plot voltage changes over time... :D

Usually multimeter functionality is implemented by sampling the voltage in analog hold, and then measuring the time differential when bleeding it off through a known resistance. (this allows for really accurate measurement with no A/D converter needed, and is easy/cheap to implement with a dedicated chip).

However with a real fast-sampling A/D conversion it woud be possible to get the waveform plot too.

Re: tohmm TOH Multimeter
 

why not? i'm just asking what i want :)

Re: tohmm TOH Multimeter
 

Sorry, I meant to add a post, not reply to yours!
Continuity beep is a good feature, yes.

However, what I'd like to have is the scope mode :)

Re: tohmm TOH Multimeter
 

See specs ^^
Note; This is not a oscilloscope. That toh will be done later with its own micro to buffer/preprocess samples.

For me that is also an A/D converter :rolleyes:

However with a real fast-sampling A/D conversion it woud be possible to get the waveform plot too.[/QUOTE]
Maximum samplerate with A/D converter selected (atm) is 860 sps.

400kHz I2C limits samplerate to about 7ksps, (at 16bits) but when taking IOCTL etc into account, maybe something like 10 sps in realtime could be doable without buffering...
(if taking samples in background for a short period of time, 860sps is doable)

Re: tohmm TOH Multimeter
 

I would really like to see a logic analyzer :)

Re: tohmm TOH Multimeter
 

Logic analyzer will be in tohscope

Re: tohmm TOH Multimeter
 

Great work kimmoli! Keep up :D