SRS Labs QMS 100 Series, Руководство пользователя

Страница: 165 / 280

RGA Command Set 3-41
Technical Reference
Important: The query response does not include the extra current (4 bytes) corresponding to the total
pressure measurement performed at the end of all histogram scans. (Please see HS command for details).
The number of points (ion currents) retuned over RS232 is calculated based on the MI and MF parameter
values. Number of points = MF - MI + 1. Each point transmitted represents an ion current and as such
corresponds to 4 bytes being received by the host computer.
The HP query is used to verify that the RGA and the host computer agree on the number of bytes that will
be exchanged over RS232 during the histogram scan.
The total number of bytes sent out to the host computer during an histogram scan is obtained multiplying
by four the number returned by the HP query.
Parameters: This command is a query, and can only have one parameter format:
HP?
Error checking:
The only acceptable parameter is a question mark.
The absence of a parameter (i. e. HP) is treated as a Bad-Parameter error.
HSparam, param:0 - 255,*
Description : Histogram Scan Trigger.
Echo: Ion Currents.
Excecute one or multiple Histogram Scans under the present scan conditions.
The scan parameter can be set for single, multiple and continuous scanning operation.
A Histogram Scan consists of as a succession of individual mass measurements (see MR command) over
a pre-specified mass range.
The mass range for the scan is set in advance with the commands MI (Initial Mass) and MF (Final Mass).
The type of detector and noise-floor settings to be used during the scan must be selected in advance with
the NF and HV commands. A current value is transmitted for each integer mass value between MI and
MF for a total of (MF-MI +1) measurements (See HP command).
For maximum data throughput, ion currents are represented as integers in units of 10
-16
Amps, and
transmitted directly in hex format (four byte integers, 2’s complement format, Least Significant Byte first).
Important:
•
Any command received by the RGA in the middle of a scan will immediately
stop the scan, halt transmission and clear the RGA’s transmit buffer.