Hanna Instruments HI 21 Series - Manual (Page 17)

33 32
Note The controller answers to the GET command with the same
data format explained in the SET command.
Following are examples of answers:
1) “03-01200”
The controller with process ID number 03 says that its
current setpoint is -1200 mV.
2) “01UHI2122210”
The controller with process ID number 01 says that it is a
HI 21222 model with firmware release 1.0.
The time-out for the first character of the controller answer is
2 seconds (except answers to PHR, MVR and TMR as ex-
plained below).
The minimum delay between the last received character and
first character of the answer is 15 ms.
The time-out for the complete controller answer to the PHR,
MVR and TMR commands is:
30 ms at 9600 bps
40 ms at 4800 bps
60 ms at 2400 bps
90 ms at 1200 bps
When the controller answers to the PHR, MVR and TMR com-
mands, the reading is sent as ASCII string followed by a
character (HI 21523 only) indicating the control and alarm
status of the controller. This character can assume the follow-
ing values:
• “A”, control and alarm are ON;
• “C”, control is ON and alarm is OFF;
• “N”, control and alarm are OFF;
For example, a possible answer to the TMR command is:
“0310.7C”
meaning that the current temperature reading is 10.7°C, the
control action is active and no alarm condition is present.
Note If the controller is not in control or idle mode and the tem-
perature reading is requested through the TMR command,
the controller answers with the last acquired reading when it
was in control or idle mode.
Note After a recognized PWD command is received, the controller
allows a maximum of 1 minute without receiving data, after
which it locks again and a new PWD command is needed to
perform password protected operations.
Following are examples of commands for setup items:
1) “03 SET 22-01200”
This command sets the setup item 22 (relay 2 setpoint) of
a mV controller, identified by the process ID number 03,
to the -1200 mV value.
2) “01 SET 33+015 ◊◊ ”
This command sets the setup item 33 (max. relay ON
time) of a controller, identified by the process ID number
01, to 15 minutes. The
“ ◊ ” character means blank.
Once the controller has received a command, it answers
with its 2-digit process ID number followed by:
• ACK (Hex 06)
If the controller recognizes the received command
and performs the requested task;
• STX (Hex 02) , Data , ETX (Hex 03)
If the received command is a request of data;
• NAK (Hex 15)
If the received command is not recognized (e.g. the
syntax is wrong);
• CAN (Hex 18)
If the controller cannot answer the request (e.g. the
password was not sent, the controller is in setup
mode, the setup item is not available in that model,
etc.)