a self powered RS 232 connection with IR reciever

[williB]

i was replacing the fuse in my radioshack multimeter and discovered the RS-232 connector had no physical connection to the multimeter whatsoever !!
it takes its power from the serial bus(pin 7)
the serial data goes just one way (out of the multimeter ).
it has a IR transmitter in the meter, powered from the meter battery, and the reciever has no connection to the multimeter
what a cool idea!!

 

[williB]

this is it
that is the IR reciever at the bottom left

 

[evandude]

In other words, it's optoisolated. That sounds like something that would be (or at least should be) done on any multimeter with a PC interface. Multimeters can suffer a lot of abuse, and be connected to some pretty dangerous voltages without issue, but a PC's serial port isn't nearly as forgiving.

Granted, It's still kind of interesting in that the boards are actually physically separated and the IR tx/rx are actually separate devices. The closest I've seen to that is a board that has a routed slit cut nearly all the way across, separating the "dangerous" side from the interface side, and then using those common 4-pin optoisolators as the only thing bridging the gap.

I guess radioshack wins some cool points for taking it to an extreme like that.
However, (going off on a tangent) they definitely lose some cool points if you actually read the documentation for the format of their serial communication with those meters... rather than simply sending the reading as some basic ASCII characters or something (so they'd be really easy to use on the receiving end), they literally send the status of all the display segments, with each of the possible display segments representing one bit, sent as a big string of bytes. Then you have to receive all that crap, pick out the bits you need, decode it to get the actual digits and figure out the range and measurement type (current, voltage, resistance, etc), and then finally be able to do something useful with it.

 

[Nigel Goodwin]

I guess radioshack wins some cool points for taking it to an extreme like that.
However, (going off on a tangent) they definitely lose some cool points if you actually read the documentation for the format of their serial communication with those meters... rather than simply sending the reading as some basic ASCII characters or something (so they'd be really easy to use on the receiving end), they literally send the status of all the display segments, with each of the possible display segments representing one bit, sent as a big string of bytes. Then you have to receive all that crap, pick out the bits you need, decode it to get the actual digits and figure out the range and measurement type (current, voltage, resistance, etc), and then finally be able to do something useful with it.

You can hardly blame RadioShack - they don't make them, and almost certainly don't design them, they just buy them from China!.

I've got a small meter with an RS232 interface, I don't know if it's isolated or not? - but the serial data doesn't sound as bad as that, although it is a bit strange?, I'll have to look further one day.

 

[evandude]

You can hardly blame RadioShack - they don't make them, and almost certainly don't design them, they just buy them from China!.

I still blame them, because it's still their decision what they buy and sell But oh well, supply and demand I guess...

Though their meters aren't as overpriced as most of their products are, I've still never considered them to be a good value for the price, as the ones from (for example) sears/craftsman are in the same price range but are generally nicer. Or maybe it's just that I'm embarrassed to own anything with the Radio Shack logo on it

 

[Nigel Goodwin]

Or maybe it's just that I'm embarrassed to own anything with the Radio Shack logo on it

Not a problem here!

 

[williB]

Granted, It's still kind of interesting in that the boards are actually physically separated and the IR tx/rx are actually separate devices.

thats what i mean

when i took the back off the serial connector came off , with the back!
i said , hmmmm
how did they connect the serial connector to the meter output?
upon further investigation , i found out
the data that comes out of the meter to the pc , can be stored in a file i think

 

[Sceadwian]

Radio Shack will NEVER get any cool points. Any such 'neat' feature of any device they sell is if nothing else a complete accident =>