8.1 RS communication protocol for LAMBDA MASSFLOW gas flow controller
8.1.1 Format of data sent by the PC to the pump and back
Data sent by the PC: #ss mm a ddd qs c
Data sent back by the mass flow controller: <mm ss a ddd qs c
where,
| # | is the first sign of a command sent by PC (master) |
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| < | is the first sign of a message sent by mass flow controller (slave) |
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| ss | is the address of the mass flow controller |
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| mm | is the address of the PC |
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| r | set gas flow (when sent as a command) |
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| r | indicates positive flow value (when received from the massflow) |
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| l | indicates negative flow value (when received from the massflow) |
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| ddd | is the gas flow rate (3 ASCII numbers from 0 to 9; sent from the highest order digit to the lowest order digit) |
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| qs | is the control sum in HEX format (2 ASCII signs of the type 0…9ABCDEF) |
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| c | is the end sign cr (carriage return) The gas flow controller will fulfill the task and block any manual command on the pump front panel. |
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8.1.2 Commands not containing data
| # ss mm g qs c | activates the local command of the gas flow controller |
| # ss mm s qs c | the gas flow is stopped (gas flow rate 0) |
| # ss mm G qs c | to send the measured gas flow rate to the PC |
| # ss mm M qs c | to send the measured gas flow rate to the PC (the same as G) |
| # ss mm V qs c | state of the gas flow controller (reads the set value) |
The commands M and G correspond to a flow rate range of 000 to 500 ml/min (in 1 ml/min steps).
8.1.3 Checksum control
The PC sends: #0201r123EEcr
The control sum (checksum) qs is made in the following way (only the last byte (2 ASCII characters of the type 0…9ABCDEF) is taken):
| # | 0 | 2 | 0 | 1 | r | 1 | 2 | 3 | EE (last
byte) | cr |
| 23h | +30h | +32h | +30h | +31h | +72h | +31h | +32h | +33h | =1EEh | 0Dh |
8.1.4 Format of the data transmission
Speed: 2400 Bd (Baud)
8 data bits, odd parity, 1 stop bit
8.2 Examples
Address of the PC: 01
Address of the gas flow controller: 02
The PC sends: #0201r123EEcr
The gas flow controller will set the flow rate to 123
The PC sends: #0201V0Bcr
The answer of flow controller (set value): <0102r12307cr
The PC sends: #0201G2Dcr
The answer of the measured (positive) flow rate: <0102r12206cr
The PC sends: #0201s59cr
The gas flow controller stops (gas flow rate is 0).
The PC sends: #0201g4Dcr
The mass flow controller will go to the local command (front panel is activated).
8.3 How to set the MASSFLOW gas flow controller address?
Please refer to the section 3.4 Setting up the address for PC control.
The digital control requires an attribution of an appropriate address to the MASSFLOW. To look up/modify the instrument address, pull out the power supply cable from the rear of the MASSFLOW. Press and hold the SET button while plugging the cable into the socket again.
The front panel illuminates and the display shows “A00”. Release the SET button. This number from 00 to 99 is the current address of the powder dosing instrument. To change the address press the buttons Λ Λ Λ under the display until the desired number is obtained.
To confirm and save the address, press the ON/OFF button.
8.4 RS-connection scheme
The 8-pole DIN connector “REMOTE” is used for the remote control and RS-485 connection. When the optional RS-485 interface is available the pins are used as follows:
| No. | Colour | Description |
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| 1. | yellow | (+) input remote flow control 0-10V *) |
| 2. | grey | pulses (1 pulse = 5 ml of gas for MASSFLOW 5000 and 0.5 ml for MASSFLOW 500, 0 and 12V) |
| 3. | green | earth, 0 V |
| 4. | brown | + 12 V |
| 5. | white | (+) input remote ON/OFF; 0V = ON, 3–12 V = OFF (this logic can be inversed on demand) |
| 6. | pink | earth, ground (GND) |
| 7. | red | RS 485 B (-) |
| 8. | blue | RS 485 A (+)
*) (zero line connected to the contact no. 3) |
8.5 RS communication protocol for the on-board INTEGRATOR (optional)
8.5.1 Communication between the PC and the INTEGRATOR of the LAMBDA instrument
From the PC to the INTEGRATOR: #ss mm z qs c
From the INTEGRATOR to the PC:
<mm ss = qs c (confirmation of the reception of a command)
<mm ss dddd qs c (sending of the requested data)
where,
| # | is the first sign of a command sent by the MASTER (PC) |
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| < | is the first sign of a message sent by the SLAVE (INTEGRATOR) |
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| ss | is the address of the subordinate station (address of the instrument with integrated INTEGRATOR) |
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| mm | is the address of the commanding station (PC) |
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| z | is a command (see below): small letters indicate a command, capital letters request data transfer from the subordinate station |
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| = | confirmation of reception |
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| aa | new address of the subordinate station (ss) (two numbers and possibly other ASCII characters A B C D E F) |
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| dddd | transferred data (values are two bytes in hexadecimal form. Single bytes are transformed into two ASCII characters 0,..,9,A,B,C,D,E,F) |
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| qs | is the control sum (obtained by the addition modulo 256 of binary values of all preceding characters including the leading sign) in HEX format (2 ASCII signs of the type 0…9ABCDEF) |
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| c | is the end sign cr (carriage return) |
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8.5.2 Commands for the INTEGRATOR
| n | reset (sets the INTEGRATOR to zero) |
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| i | start of integration |
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| e | stop of integration |
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| I | sends the integrated value (positive-negative) |
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| N | sends the integrated value “I” and sets the integrator to zero (both registers) |
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| R | sends the integrated value of the positive flow (2 bytes HEX = 4 ASCII) |
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| L | sends the integrated value of the negative flow (2 bytes HEX = 4 ASCII) |
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8.5.3 Examples
Address of the PC: 01
Address of the instrument with on-board INTEGRATOR: 02
The PC sends: #0201I2Fcr
The control sum (checksum) qs is made in the following way (only the last byte (2 ASCII characters of the type 0…9ABCDEF) is taken):
| # | 0 | 2 | 0 | 1 | I | 2F (last byte) | cr |
| 23h | +30h | +32h | +30h | +31h | +49h | =12Fh | 0Dh |
The PC sends: #0201i4Fcr
i.e. in hexadecimal form: 23h 30h 32h 30h 31h 69h 34h 46h 0Dh
This means: For a subordinate station (SLAVE) with address 02 from commanding station (MASTER) with address 01
Start of integration
The control sum is 14Fh (last byte: 4F); end of message cr (carriage return)
The INTEGRATOR answers: <0102=3Ccr
The PC sends: #0201N34cr
The INTEGRATOR answers: <0102N03C225cr (integrated value is 03C2h) and resets to zero
The PC sends: #0201e4Bcr
The integration will be stopped and the command will be confirmed.
The INTEGRATOR answers: <0102=3Ccr