Calibration - Valeport 801 EM Operating Manual

6. Calibration

Selecting DIRECT EM COMMS at the OPTIONS MENU enables the user, using a PC in terminal mode
via the optional DC data lead to read and alter the EM calibration.
Connect the unit to a PC via the data interface lead supplied. Connection details are given in
Section 4.6.3.
Run a terminal emulation program on the PC, ensuring that communications are correctly set to
4800 baud, 8 data bits, 1 stop bit, no parity bits, flow control NONE.
The EM calibration has 3 parts to it:
HYDRO CAL
SYSTEM GAIN FACTOR
SYSTEM ZERO OFFSET
Having connected up the CDU and PC and entered DIRECT EM COMMS, the unit will output EM
data at a rate of 2 Hz. Calibrated data from the EM electronics is in mm/sec. To communicate to
the unit and interrupt it, press and hold the "#" key on the PC. When the unit responds with a §,
enter a single # and press <cr>. The unit will respond with a "«" [this may not be visible in all
terminal programs if the font is not available] and then await a command. These commands are
a series of "#" codes
Code Followed By space and
#007 Output_Format<cr>
#030
#028
#170 Zero_offset<cr>
#172
#174 Gain_Factor<cr>
#176
#190
#192 Calibration<cr>
If the user wishes to alter the calibration from the factory setting, it is necessary to enter the
calibration coefficients. The calibration coefficients are stored within the micro-controller in an
ASCII text string. The format of this string depends on the type of calibration (line fit or polynomial
fit). The first part of the string will be the calibration function number, selected from the table
This is the "shape" of the calibration curve and for normal routine
calibrations the same calibration is used for all units of the same
type.
The Gain Factor is specific to a combination of sensor and CDU, and
is the factor by which all raw data from the electronics are multiplied
to normalise the data to a standard counts per metre/sec.
The Zero Offset is specific to a combination of sensor and CDU, and
the number of counts which the unit outputs at zero flow. See
section 6.1 below for details on re-setting zero offset.
Nothing<cr>
Nothing<cr>
Nothing<cr>
Nothing<cr>
Nothing<cr>
Operation
Sets the output format of the unit to CAL or NOCAL.
CAL is data in calibrated units, NOCAL is raw counts
and is used for calibrating purposes
Reads the output format CAL or NOCAL
Sets the unit into run mode. Data is outputted at the
Sets the zero offset in counts
Reads the zero offset which has been set
Sets the GAIN_FACTOR
Reads the GAIN_FACTOR which has been set
Reads the Hydro Calibration which has been set
Sets the Hydro Calibration
Calibration
2Hz rate.
© 2016 Valeport Ltd
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