AMI has identified incompatibilities with National Instruments IEEE-488 cards that require a ROM fix for our liquid helium level instruments (Models 134, 135, 136 and 137). The problems appear to be unique to NI’s cards. The problem manifests itself as unrecognized commands after sending the first command. The first command sent to the instrument after a Device Clear functions correctly, however, any subsequent commands fail.
Your instrument is in need of a ROM upgrade if the ROM is dated before 2/27/95 and you need IEEE-488 communications capability using a National Instruments card. Contact AMI for a ROM upgrade at no charge.
Step-by-step procedure for installing the new ROM
This procedure is to be performed only by personnel familiar with electrical safety precautions and the safe handling of static sensitive devices. Before removing the cover of the instrument, remove the power from the instrument by disconnecting the power cord from the power receptacle. Failure to do so could expose the user to high voltages and potential life-threatening electrical shock.
1) De-energize the instrument and remove the cover.
2) Using an IC extraction tool or a thin flathead screwdriver, gently remove the ROM chip from the main board. The ROM chip is labeled as HBUSC8W 4/30/92 8:24am on the main board. The U7 socket illustrated on page 16 of your new manual shows the relative location of the ROM on the main board. Note that the notched end of the ROM is aligned with the notched end of the U7 socket.
3) Gently insert the new ROM chip labeled he_2.0: 2/27/95 into the U7 socket. Be sure to align the notched ends of the ROM and socket. Be sure to insert the ROM into the socket until firmly seated.
4) Replace the instrument cover, connect the instrument to a power receptacle, and power on. The new ROM is ready for use.
Changes to the communication command set
The FINISHED command has been eliminated from the RS-232 and IEEE-488 command sets. The instrument will not respond to external communication until a measurement in progress is completed. As a result, the FINISHED command would always indicate the measurement has completed since the reply was blocked until the measurement was completed. Therefore, the FINISHED command is unnecessary since the receipt of a reply from the instrument is sufficient indication of a completed measurement cycle.