corresponding to a MEASure:ARRay?, READ:ARRay?, or INITiate with
TRIGger:COUNt > 1.
- For the THM1176, try to build a CALibration sequence with a zero-gauss
chamber into the beginning of any lengthy measurement sequence. The
THM1176 is designed to have very low offset and offset drift, but as with any
Hall device, these remain a significant source of error. Note that this does not
apply to the TFM1186 – See Section 2-6.
- After an INITiate command with TRIGger:SOURce = BUS, the instrument
expects TRIGger:COUNt triggers before resuming normal operation. During
this interval, the following commands are illegal: CALibration:INITiate, FETCh,
INITiate:IMMediate:ALL, SENSe:FLUX:RANGe:UPPer,
SENSe:FLUX:RANGe:AUTo. The following commands are legal, but cause an
ABORt and therefore terminate the acquisition sequence: *RST, ABORt,
MEASure, READ.
- INITiate:CONTinuous is used for TRIGger:SOURce = TIMer or BUS, to avoid
losing triggers while data is read out.
- Using the *OPC command, you can generate a ReQuest for Service (RQS)
when a measurement (or any other action) is complete. Set bit 0 of the
Standard Event Enable register and the ESB (Event Summary Bit) in the
Status Enable register. Now, the execution of an *OPC command will generate
an RQS.
- Alternatively, set bit 4 (MAV = Message AVailable) in the Status Enable
register and append the *OPC? command to the previous commands. This will
generate an RQS because *OPC? places a “1” on the output.
- If you program the instrument to generate an RQS, it is very important to
Enable Service Requests on the host. This posts a read on the appropriate
USB endpoint, the Interrupt endpoint. In the USB protocol, the host initiates all
transfers; so if the host has not posted a read, the instrument cannot complete
its RQS transfer. This will block the Interrupt endpoint, and any other
commands using this endpoint – notably the USBTMC-USB488 Read Status
Byte function – will fail.
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