MKS 979B Atmosphere to Vacuum Transducer

C=I 2/(1 × 10 7) (Farads), R=E/I a (ohms, where a=1+(50/E)), and R is at least 0.5 Ω and C is at least 1.0 × 10 ⁻⁹ F.

Operation control

1. Control and status pin operation

Degassing on (Pin13): Enable degassing when grounded, with priority higher than DG command or degassing button; After 30 minutes of degassing, it is necessary to disconnect and reconnect to restart degassing, and degassing should not exceed 30 minutes every 4 hours.

Degassing state (Pin9): When degassing is closed, it is open circuit/suspended, and when it is open, it is grounded; An external pull-up resistor with ≤ 24 VDC can be connected, and the current should be less than 15mA.

Filament selection (Pin10): By switching the active filament on/off the power supply, the state can be switched instead of selecting a fixed filament.

2. Factory default settings

The sensor parameters are preset to default values, including: active filament 1, address 253, baud rate 9600, degassing power off, automatic emission current (20 μ A>1 × 10 ⁻⁴ Torr, 1mA<1 × 10 ⁻⁴ Torr), control set point enabled, filament power off, gas correction 1, gas calibration type nitrogen, 3 set points disabled, hysteresis value 1.10E0 Torr, set point value 1.00E0 Torr, set point direction "below (BELOW)", protection set point 1.0E-2 Torr, unit Torr, analog output DAC1, RS485 test off, RS delay on.

3. RS-485/RS-232 communication protocol

Basic parameters: Supports baud rates of 4800-112200 (default 9600), data format of 8-bit data bits, no checksum, and 1-bit stop bit; RS-485 is a half duplex two-wire system, which is the same protocol as RS-232.

Address rule: Standard address 001-253 (default 253); Universal address 254 (used for communication with unknown address devices, will respond), 255 (broadcast address, executes commands but does not respond, such as batch modification of baud rate).

Command syntax: The query format is @<device address><query command>?; FF (such as querying baud rate: @ 253BR?)?; FF）， The command format is @<device address><command instruction>! <Parameters>; FF (such as changing the baud rate to 19200: @ 253BR! 19200; FF）； The response starts with ACK (success) or NAK (failure), and the NAK code corresponds to different errors (such as 160=unrecognized message, 169=invalid parameter, 172=value out of range, etc.).

4. Core Command Set

The commands are divided into five categories: setting, status, pressure measurement and degassing, set point, and calibration. The core commands are as follows:

Command Type Command Identification Function Description Example

Set command AF (active filament) to query/select 2 filaments (value 1/2) of the hot cathode sensor. Query: @ 001AF?; FF; Setting: @ 001AF! 2; FF

AD (Address) Query/Set Device Address (001-253) Query: @ 254AD?; FF; Setting: @ 001AD! 002; FF

BR (baud rate) query/set baud rate (4800/9600, etc.) query: @ 001BR?; FF; Setting: @ 001BR! 19200; FF

DAC (Analog Output) Query/Set Analog Output Type (1=DAC1, 2=DAC2) Query: @ 001DAC?; FF; Setting: @ 001DAC! 2;FF

FD (factory default) restores all user calibration values to factory default command: @ 001FD!; FF

Status command DT (device type) query device type response: @ 001ACKMP-HC 979B; FF

FS (filament status) query for the on/off status of the active filament: @ 001FS?; FF

FV (firmware version) query firmware version response: @ 001ACK1.00; FF

SN (serial number) query device serial number response: @ 001ACK0000012345; FF

T (sensor status) query hot cathode status (F=filament fault, G=hot cathode on, etc.) Response: @ 001ACKO; FF (O=normal)

Pressure measurement and degassing FP (filament power supply) switch filament power supply (only effective when the control setpoint is disabled, disabled when the pressure is greater than 5 × 10 ⁻ Torr) command: @ 001FP! ON; FF

DG (degassing power supply) switch degassing (pressure must be<1 × 10 ⁻⁵ Torr, automatically shuts off after 30 minutes) query: @ 001DG?; FF; Setting: @ 001DG! ON; FF

PR1/PR2/PR3 (pressure readings) respectively read MicroPirani (PR1, above 1 × 10 ⁻³ Torr), hot cathode (PR2, below 1 × 10 ⁻⁴ Torr), and combined reading (PR3, full range). Query: @ 001PR1?; FF; Response: @ 001ACK1.23E-2; FF

The set point command SPx (set point value) queries/sets the pressure values (Scientific notation) of the three set points: @ 001SP1! 1.00E-3; FF

SDx (Setpoint Direction) Query/Set Setpoint Direction (BELOW/ABOVE) Setting: @ 001SD1! ABOVE; FF

SHx (hysteresis value) query/set the set point hysteresis value (to avoid relay jitter and match direction) setting: @ 001SH1! 1.10E-3; FF

ENx (Enable Setpoint) Enable/Disable 3 Setpoint Commands: @ 001EN1! ON;FF

Calibration command ATM (atmospheric pressure calibration) to calibrate MicroPirani to full range (requires ventilation to atmospheric pressure, stable for 20 minutes) Command: @ 001ATM! 7.60E+2; FF

VAC (vacuum calibration) calibration MicroPirani zero point (needs to be drawn to<1 × 10 ⁻⁴ Torr, stabilized for 20 minutes, automatically calibrated when hot cathode pressure<1 × 10 ⁻⁴ Torr) command: @ 001VAC!; FF

GT (gas type) query/setting MicroPirani's measurement gas (nitrogen/air/argon, default nitrogen) setting: @ 001GT! ZEROGEN; FF