Newsgroups: comp.sys.hp48

Here is a first hand review of the ADCM-48 Computer Interface Module.  I'm
sorry to see that EduCALC has dropped it from their catalog.  It still exists,
however, and is definitely worth buying.

Regards
Ray Depew
Hewlett Packard Co, Fort Collins, Colorado
rrd@hpfiqa.fc.hp.com 
DISCLAIMERS:  I am not connected with Travtech in any way.  I'm not getting
paid to do this.  I don't speak for HP, and this is not an official HP
endorsement of the ADCM-48.

------------------------------------------------------------------------
                   Review of the Travtech ADCM-48
                      Data Acquisition Module
                            Ray Depew
                          July 30, 1992


SUMMARY

   I got to use the Travtech ADCM-48 data acquisition module for a while
   with my HP48SX.  It's a great little box for laboratories, 
   hobbyists and anyone needing to take periodic readings of electrical or 
   physical conditions.  It's easy to use, robust in design and very
   versatile.  It is small, light and portable.  The documentation includes 
   everything you need to know to use the device, even drawings of various 
   sensor configurations.  The price is unbeatable.

WHAT SETS IT APART

   The ADCM-48 is a unique, low-cost alternative for those who wish to do 
   data acquisition and control with an HP48S/SX.  Unlike most (all?) other 
   data acquisition hardware currently on the market, the ADCM-48 is powered 
   by a 9-volt battery, and communicates with its host via infrared.  It
   uses a low-power microprocessor, and it uses a host of pwer-saving
   "tricks" to stretch out that 9-volt battery as far as it will go.
   It packs a lot of power into one tiny, portable box.

PHYSICAL DESCRIPTION

   The ADCM-48 is in a black plastic box, of a texture similar to the HP48
   case.  It's only a little larger than a pack of cigarettes.  (No, I don't 
   smoke.)  Its IR trasmit/receive diodes and internal circuitry are visible 
   through a red plastic window on one end of the case.  The battery
   compartment is accessed via a sliding door on the bottom of the other end.
   All the electrical connections and a green "on-line" LED are located on
   the top of the case.  The connections are clearly and unambiguously
   marked.

CAPABILITIES & APPLICATIONS

   Well, I hate to just regurgitate the manufacturer's specs here, but I hate 
   to leave anything out, either.  So here's the Overview, lifted from the 
   owner's manual (typos are mine):

      "The purpose of teh ADCM-48 is to provide low cost, completely 
      portable basic digital and analog I/O capabilities for the HP 48 
      calculator.  The system provides the most commonly used 
      instrumentation I/O functions in a small, battery powered accessory 
      instrument.  The ADCM-48 provides 4 zero to five volt eight-bit 
      analog input channels, 4 TTL/CMOS compatible digital inputs and 4 
      high current (.5 amp) outputs.  The first digital output is also a 
      1 KHz pulse width modulator output [which can double as an 8-bit 
      D/A converter if you add a filter on the end].  The power for the 
      unit is provided by an internal 9 volt battery.  The power drain is 
      very low and with creative use of the alarm functions of the HP48 
      and ADCM-48 sleep mode, a remote data logging and control system 
      capable of several months of stand-alone operation can be implemented.  
      The unit makes no physical connection with the HP 48 and 
      communicates with the HP 48 over the infrared calculator to 
      calculator link.  This allows for setup convenience, electrical 
      safety and eliminates the risk of damage to the HP48.  Software for
      common instrumentation setups as well as low level subroutines are 
      included on disk.  Extensive application circuits for interfacing 
      to a variety of devices are included in the last chapter of this
      manual.  The user should find it simple to adapt these circuits
      and programs to his specific needs."

   I got to use the ADCM-48 for a 30-day trial period.  During that time I did 
   all the standard stuff:  measure flashlight batteries, horse around with 
   the digital inputs, and make LEDs blink and lights go dim.  The one cool 
   thing I'd like to do is combine the ADCM-48's capabilities with the 
   Stripchart and Analog Meter applications from the book "HP48 Graphics," 
   to record my attic temperature over a 24-hour period.  (I'm in the midst 
   of adding soffit and roof vents, and I want to see how well they work.)

   I was going to write a program to turn the ADCM-48 into a serial interface
   protocol analyzer, but I ran out of time.

   For scientists or engineers, this thing would be priceless in research
   or lab work.  As a ChemE or EE student, I would have found it useful in 
   any of the following places:
   -  Chem:   Physical Chemistry Lab
   -  ChemE:  Unit Operations (senior) Lab
   -  chemical analysis:  titrations, colorimetry, pH/pCl/etc.
   -  reaction kinetics
   -  thermodynamics 
   -  mechanical stress/strain testing, or properties of materials
   -  fluid mechanics or aerodynamics 
   -  solar/wind/combustion/nuclear energy  research
   -  medical electronics
   -  chemical process control
   -  VLSI fabrication process control

   One day I'd like to have a wind-powered generator on my property -- I 
   already have it planned out and everything.  A little box like this would 
   allow me to monitor and control it using only my HP48.  It could:
   -  measure wind speed and direction
   -  measure air pressure and temperature
   -  measure generator speed
   -  measure generator output
   -  measure storage battery levels
   -  apply brakes as needed
   -  switch between utility power and wind power according to wind speed

OPERATION

   Operation is a cinch.  The ADCM-48 comes with a disk containing some 
   preprogrammed examples and other useful routines.  These could be 
   combined into an HP48 library, and perhaps even rewritten in 
   machine language, but they work fine in User RPL.  The ADCM-48 takes 
   advantage of the fact that the HP48 is no speed demon, to run slower than 
   other similar units and thus preserve battery life.

   The only drawbacks I noted have to do with the use of the IR medium.  The 
   first drawback was in having to put the two machines less than a centimeter 
   apart, and the second was in adjusting the height of the HP48.  
   These are detailed in the next section.

LIKES/DISLIKES

   I like the fact that it is powered by a 9-volt battery.  This means that
   there are no adapter cables to care for, et cetera.  If you're worried
   about the battery dying at the wrong time, I would imagine that you could
   connect the battery terminals to any 9VDC power supply without problems.
   (I would also imagine you to be overly cautious.)

   I like the IR transmission medium.  There's no need to procure and modify 
   cables, connect grounds, et cetera.  The ADCM-48 can be enviromentally 
   isolated from the host computer.

   I like the datalogging option, which allows the ADCM-48 to output numbers
   directly to an HP82240B printer.  The "SCOPE" program on the included 
   disk turns your HP48 into a scope display.

   The commands are extremely simple.  The documentation is first class.

   I found that the IR transmission distance was very short.  When many 
   people are using their HP48's as television remote controls, it seems a 
   shame to hobble the machines by requiring them to be so close together.
   Other users have reported longer operating distances, so my unit may 
   not be typical.

   I had to raise my HP48 4 or 5 millimetres above the desktop to align it 
   properly with the ADCM-48.  I would prefer to see longer leads or sockets 
   used in the ADCM-48 in order to lower the diodes to the correct height.
   With a longer operating distance, this alignment would not be so critical.

RECOMMENDATIONS

   This is an exellent piece of hardware.  The only alternative that I know 
   of, the D1000/2000/3000/4000 series of blue hexagonal units sold by DGH, 
   requires four different modules to duplicate all the functions performed 
   by the ADCM-48, at a cost of about $1000, as compared to the $250 cost of 
   the ADCM-48.  While the DGH solution is more powerful, it is designed for 
   commercial/industrial use and may be more than the laboratory or hobbyist 
   needs.  I would recommend the ADCM-48 for anyone in need of low cost, high 
   performance multichannel data acquisition & control capability.

WHERE TO GET IT

   The ADCM-48 can be ordered directly from TravTech, at

	Travtech Electronic Instrumentation
	10959 Barbados Way
	San Diego, CA 92126

   Cost is $249.00, plus shipping and handling.

   It used to be available from EduCALC, but it's not in their latest
   catalog.
From: akcs.joehorn@hpcvbbs.cv.hp.com (Joseph K. Horn)
Date: Sat, 29 Aug 1992 10:40:01 GMT
Subject: Modest Diversion for Programmers
Message-ID: <2a9f465b.1627comp.sys.hp48@hpcvbbs.cv.hp.com>