Products > Test Equipment
External Display for Agilent 34401A (or any DMM with RS232 Output Stream)
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Harvs:
Nothing sounds hard, I'll keep coding and see where we end up.  I do quite like the pod idea, but don't get too worried about it having to be in a device agnostic manner.  I'm just coding in a drop down box to select the type of device you're connecting to, so any translation etc can be hidden behind that.

BTW the problem with not having streaming data, is how the tablet will know when a new reading is complete.  This is a common problem with SCPI instruments I've coded with.  On most, there's nothing you can even poll to check if a new reading is available, all you can do is get what is currently displayed on the screen which you have no way of telling whether it's a new reading with the same value or not.
Galaxyrise:

--- Quote from: Harvs on November 16, 2013, 02:43:59 am ---BTW the problem with not having streaming data, is how the tablet will know when a new reading is complete.  This is a common problem with SCPI instruments I've coded with.  On most, there's nothing you can even poll to check if a new reading is available, all you can do is get what is currently displayed on the screen which you have no way of telling whether it's a new reading with the same value or not.

--- End quote ---
The two meters I'm familiar with are the Keithley 2000 and the hp 34401a.  Both have a way to "fetch me the next number" and a "measure into a buffer which I can dump (and then clear) at my leisure".

Funny how things converge; I was going to work on a little tool drive my K2K's scanner card and generate a csv or something, but the dern thing refuses to use the rs232 port (SCPI only, it says.) 

The idea of pulling that data to a tablet over bluetooth is very appealing indeed.  However, I'm worried that the bluetooth signal will get picked up in the measurements.  I've noticed that using my cell phone nearby will add noticeable noise.  I take it you don't see that with your bluetooth link?  I wonder why not.
Harvs:

--- Quote from: Galaxyrise on November 17, 2013, 01:30:52 am ---
--- Quote from: Harvs on November 16, 2013, 02:43:59 am ---BTW the problem with not having streaming data, is how the tablet will know when a new reading is complete.  This is a common problem with SCPI instruments I've coded with.  On most, there's nothing you can even poll to check if a new reading is available, all you can do is get what is currently displayed on the screen which you have no way of telling whether it's a new reading with the same value or not.

--- End quote ---
The two meters I'm familiar with are the Keithley 2000 and the hp 34401a.  Both have a way to "fetch me the next number" and a "measure into a buffer which I can dump (and then clear) at my leisure".

--- End quote ---

Yeah I've only got Rigol gear and the Escort meter.  I understand that it's totally dependant on how the manufacturer has implemented SCPI, and hence it will require a bit more work to support each instrument if it requires specific register writes and reads.


--- Quote ---Funny how things converge; I was going to work on a little tool drive my K2K's scanner card and generate a csv or something, but the dern thing refuses to use the rs232 port (SCPI only, it says.) 

The idea of pulling that data to a tablet over bluetooth is very appealing indeed.  However, I'm worried that the bluetooth signal will get picked up in the measurements.  I've noticed that using my cell phone nearby will add noticeable noise.  I take it you don't see that with your bluetooth link?  I wonder why not.

--- End quote ---

I haven't found any issues with radiated emissions, I believe bluetooth has a lot lower peak power than a typical mobile phone, also my meter is only 5.5 digit (looking for a 6.5 digit now).  However I have added bluetooth to embedded circuits before and found the noise it puts on the power rails to be horrendous (obviously this will be module dependant.)  So now I'm always sure to put the BT module on it's own separate regulator if I intend on using the uC's internal ADC.

As far as the bench meter goes, the BT module is at the back of the instrument, outside of the metal enclosure and away from anything it could couple into.  So no, I've seen no ill effects.
quantumvolt:

--- Quote from: Harvs on November 16, 2013, 02:43:59 am ---...

BTW the problem with not having streaming data, is how the tablet will know when a new reading is complete.  This is a common problem with SCPI instruments I've coded with.  On most, there's nothing you can even poll to check if a new reading is available, all you can do is get what is currently displayed on the screen which you have no way of telling whether it's a new reading with the same value or not.

--- End quote ---

The 34401A has trig and measurement complete on separate plugs.

Nice to see that quite a few people works on this now. I am slow, but am working on it. May be I'll have BT next Christmas  ;D

The other day I used serial data from the 34401A (current) and SPI-to-serial data from the LTC2400 24 bit ADC (voltage) in order to measure some precision resistors. As I needed to divide measurement pairs I read both datasets to an Arduino for math before sending all three datasets to the PC via USB and into a Processing sketch presenting V,I and R (one screen - from 2 instruments).

Point is - with a large tablet screen and a uC in between the instruments and the bluetooth transmitter you can send many datasets that goes into a summary screen or several small windows/GUIs on the tablet.
bingo600:
@Harvs

Nics app  :-+
This is taking an interesting turn  :)

I'd prob. also worry a bit about BT in the Lab , but only because i know GSM to disturb volt refs. quite a bit.

But i do have a feeling that GSM is quite gigh wattage , where BT and the WiFi coverage i have in there isn't.
So i guess the BT isn't a problem for normal lab usage.

Another way to make a cheap/easy "bus" would/could be RS-485 or I2C , and then convert that to RS232 just before hitting the tablet.

/Bingo
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