Flintec LDU 68.2 - Manual (Page 18)

LDU 68.1 & 68.2 Technical Manual, Rev. 12 January 2010 Page 18 of 28
8.5. Taring and Zeroing Commands – SZ, RZ, ST, RT
The following commands allow you to set and reset the zero and tare values. The zero set up during calibration
remains the ‘true zero’ but the new ‘current zero’ can be set up by using the SZ command. If the SZ command
is issued and accepted then all weight values will then be based on the new ‘current zero’. Please remember
that the zero value will be subject to the Zero tracking function if enabled.
If the weight signal is not stable (as defined by the No motion range NR and the No motion time NT) then both
the set zero SZ and set tare ST commands will be disabled.
Also the Set Zero SZ command is not allowed if the new zero value required and the ‘calibration zero’ differ by
more than 2 % of the CM value (maximum allowable value).
See chapter 9 Used in “Approved” applications.
8.5.1. SZ Set Zero
This command sets a new “current zero” which is then the basis of all weight values until further updated by the
zero tracking function, another SZ command or the “reset zero” command RZ.
Master (PC / SPS) sends Slave (LDU XX.X) responds Meaning
SZ
 OK Set zero performed
The SZ command will fail (LDU responds with ERR) if the new “current zero” is more than 2% (of the CM value)
higher or lower than the “true zero” set during calibration. The SZ command will also fail if the weight signal is
not stable as defined by the No motion range (NR) and the No motion time (NT). If the weight signal is “stable”,
the response to the IS command (Device Status) will show the “signal stable” bit active and the SZ command
will be accepted (OK). If the “signal stable” bit is not active, the SZ command will be rejected and the LDU will
respond with ERR (error).
8.5.2. RZ Reset Zero Point
This command cancels the SZ command and the zero reading reverts to that set by the CZ command during
calibration.
Master (PC / SPS) sends Slave (LDU XX.X) responds Meaning
RZ  OK Zero point CZ active
The LDU responds to the RZ command with either OK or ERR. If OK is returned then the “zero action
performed” bit in the Device Status (IS) response will be set to “0”.
8.5.3. ST Set Tare
This command will activate the net weighing function by storing the current weight value as a tare.
The weight signal must be “stable” within the limits set by NR (No Motion Range) and NT (No Motion Time)
commands for the “signal stable” bit to be active and set tare command to be accepted.
Master (PC / SPS) sends Slave (LDU XX.X) responds Meaning
ST  OK Tare performed / Net operation
If the weight signal is “stable”, the response to the IS command (Device Status) will show the “signal stable” bit
active and the ST command will be accepted (OK). If the “signal stable” bit is not active, the ST command will
be rejected and the LDU will respond with ERR (error).
8.5.4. RT Reset Tare
This command resets the tare and the weighing signal returns to gross mode.
Master (PC / SPS) sends Slave (LDU XX.X) responds Meaning
RT  OK Tare de-activated / Gross operation
The LDU responds to the RT command with either OK or ERR. If OK is returned then the “tare active” bit in the
Device Status (IS) response will be set to “0”.