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From: rrd@hpfcso.FC.HP.COM (Ray Depew)
Newsgroups: comp.sys.handhelds
Subject: Re: HP 48 Data Aquisition
Message-ID: <7360070@hpfcso.FC.HP.COM>
Date: 15 Feb 91 07:20:13 GMT
References: <2520@bnlux0.bnl.gov>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 63

In hpfcso:comp.sys.handhelds, geller@bnlux0.bnl.gov (joseph geller) asks:
>>>>>>>
	Is anyone using the HP 48SX for data acquisition?  I'm thinking of
using mine to do some data logging via the RS 232.  I only need 4 or 5 data 
points (12-14 bit) every one to 5 minutes.

	I'm giving some thought to some sort of used chart recorder with 
RS 232 output (lot's of them have it now) or building a simple Analog to 
Digital Converter circuit to do the job myself.
>>>>>>>

There are some terrific units that will meet your needs, sold by DGH and by
Omega Engineering.  Actually, they're built by DGH and OEM'ed by Omega.
I think technical support is the same either way, but....

ANYway, these are little blue hexagons, about an inch thick and less than 4
inches in diameter, called "Signal Conditioning Modules."  Basically, they're
a D/A converter, a UART, some glue logic and an EEPROM all wrapped up in 
a watertight box.  They take 10-30 volts unregulated DC for power, and do
all the power conditionnig themselves They come factory-preconfigured for
300 baud, so you have to hook them to a non-HP48 computer to change them to
a baud rate the 48 can recognize.  If I remember correctly, they go all the
way up to 19.2 Kbaud.

The I/O for them is written such that you can daisy-chain the RS-232
modules together (very much reminiscent of HPIL -- maybe what HPIL aspired
to be).  The RS-485 models are meant to be connected in parallel, through
an RS232/RS485 convertor box ($99, or build your own).  Either version uses
exactly the same commands, and they're really easy to learn.  For example,
to read data from the first module in line, you send it the command "#1RD".
THat's all.

The only problem with them is that they can't read the HP48's low voltage 
signals directly.  They're available with either RS-232, RS-422 or RS-485
interface, and I always used the RS-485 models, with a 232/485 convertor
between the modules and the 48.  The convertor seemed to boost the signal
quite nicely.

You can use the RS-232 versions just fine, if you build a little power booster
to boost the 48's signal to something acceptable.  Joel Kolstad built a 
really nice booster, and I was going to write an app note for HP for it, but
his prototype is still sitting on my shelf (blush of embarrassment here).

Prices range from about $200 for the voltmeter to about $400 for the
frequency counter.

If you send me email, I'll send you addresses for DGH and Omega.

(It's on my list, Joel, I just ahven't gotten around to it yet!)

There's a really nice book coming out soon, with a couple of cool programs
about turning your 48's display into either a stripchart recorder or an
analog meter ---- and turning your 82240B printer into a stripchart recorder.
THe author is a close personal friend of mine.

Please excuse the typos.  I'm typing this in by modem, over a VERY noisy 
phone line.


Regards
Ray Depew
IC's by Bill and Dave   
rrd@hpfitst1.hp.com