                         HP8903B Response.exe Version 1.48
                     (A buggy, but improving, work in progress)
        Program & Notes are Copyright 2010 Conrad R. Hoffman, All Rights Reserved


Disclaimer:
The program tries to be gentle with your power amplifiers, but it's also capable of destroying them if you
enter too stressful a test. I assume absolutely no liability for loss or damage of any type as a result of
the use of this program. It is supplied free with no warranty or guarantee of any type, including suitability
for any purpose. All risk is assumed by the user. If you cannot accept full responsibility for damage to the
8903B analyzer or any device connected to it, any damage to the Prologix interface, or any damage to the
computer itself, or any personal injury, do not use this program! Use of the program implies acceptance of
these terms. Use the best accepted safety practices around high voltage or high current circuits.

Intro:
This is a control program for the Hewlett Packard 8903B Audio Analyzer. It automates the scanning for response
and THD. It is specific to the Prologix GPIB interface adapter and will not work with anything else. It uses
the FTDI dll for the chipset in the Prologix device, so that has to be installed on the target computer system
for this program to work.
A good source for the Prologix adapter is Spark Fun Electronics (Google 'em).

HP8903B Response.exe stands alone and can be placed in any directory. It will create its own ini file in
whatever directory it happens to be in. Make a desktop shortcut.

Notes:

1. The 8903B should be at the factory default address of 28. The Prologix should be 0. If you absolutely have
   to use some other addresses, or want to run two instances of the program on two 8903B units, you can tell
   the program to use different addresses by including them on the command line: "HP8903B Response.exe 28 0". A
   message will be displayed on startup confirming the new addresses and letting you know you've entered them
   correctly. Entering command line parameters in a desktop shortcut can be done, but I remember it as being a
   bit fussy. The exact information on how to do is is scattered about on-line.

2. Limit yourself to the inputs in the drop down boxes as far as numbers of scanning points. Understand the
   scanning limits from the 8903B manual. It's ok to enter any voltages you want. Enter any response graph
   scaling you want in the boxes at the bottom of the screen.

3. Voltages are amplifier OUTPUT! The program will figure out the necessary gain and set the input accordingly.
   This allows the power to be calculated- it is not measured, just displayed for convienence.

4. Connect your 8903B input to output to check the response, THD and signal to noise. It doesn't put out much
   voltage, so 1V or so is the limit.

5. Scanning a huge number of points/decade can take forever and accomplishes very little unless you're analyzing
   filters.

6. The program now uses an ini file to store the model, serial and comments for printing. The printout header
   isn't entered in the program, but you can change it in the ini file. Just edit the ini file using Notepad. If
   you mess it up, delete the ini file and the program will create a new one.

7. The vertical scaling is now live. As you change it in the drop down boxes the graph text will be updated
   immediately. Previous scans cannot be updated. If you change the scanning frequencies, the previous scans will
   not be rescaled, so use the graph clear button as needed!

There are many known issues with this program and doubtless many as yet unknown issues. A partial list follows:

1. The math for horizontal log scale divisions in the graph and the printed graph is a bit buggy. It works best
   with a 20-20000 Hz scan range, or other "sensible" limits so you can tell what frequencies the lines represent.
2. There is yet no way to abort a scan.
3. There is yet no way to automatically disconnect the GPIB connection and go back to manual operation.
4. You can probably enter illegal values that the 8903B won't understand or exceed its scan capability.
5. There is no error checking on your entries.
6. Changing graph scales will not rescale previous traces.
7. Every now and then the program won't detect sufficient level and will abort the scan. I do not know if this
   is unique to my 8903, or some random glitch with the program. Just scan again and it usually works fine.
8. If my Prologix is connected during computer boot up, it won't communicate. Just unplug and replug the USB.
9. I tried a version using a bitmap of the screen to simplify printing, in particular to solve some of the math
   and scaling problems I was having. That didn't work for all users. This version goes back to creating the
   graph line by line. It should work great for all users, but keep an eye out for horizontal scaling errors with
   the vertical lines on the graph!

Someday more notes will follow, but right now this is a work in progress. Check the website periodically for
new versions. Don't bang your head against a wall- if you can't get this to work, send me an email.

Conrad Hoffman
choffman@rpa.net
http://www.conradhoffman.com
