AMALGAMATED INSTRUMENT PM4-IVT, Operation And Instruction Manual, Page: 42 / 45

6.2 Offset calibration
CAL OFSt
- Calibration offset - the calibration offset is a single point adjustment which can be
used to alter the calibration scaling values across the entire measuring range without affecting the
calibration slope. This method can be used instead of performing a two point calibration when
a constant measurement error is found to exist across the entire range. To perform a calibration
offset press the
^
and
v
buttons simultaneously at the
CAL OFSt
function. A “live” reading
from the input will be seen, make a note of this reading. Press the
F
button, the message
SCLE
will now be seen followed by the last scale value in memory. Use the
^
or
v
button to adjust the
scale value to the required display value for that input. For example if the “live” input reading
was
50
and the required display value for this input was
70
then adjust the
SCLE
value to
70
.
Press the
F
button to accept changes or the
P
button to abort the scaling. If the scaling has
been accepted the message
OFSt End
should be seen. If the
ZERO RNGE Err
message is seen
refer to the
ZERO RNGE
and
CAL ZERO
functions.
6.3 Zero range
ZERO RNGE
- Zero Range - the zero range function allows a limit value to be set (in engineering
units) above which the display will not zero i.e. if a zero operation is attempted via the
P
button,
remote input or set zero function when the display value is greater than the zero range setting
the display will refuse to zero and give a
ZERO RNGE Err
message (note that the
CAL OFSt
function is also affected by the
ZERO RNGE
setting). For example if the zero range setting is
10
the instrument will only respond to a zero operation if the display reading at the time is between
-10
and
10
. If the zero range function is not required it can be set to
OFF
by pressing the
^
and
v
buttons simultaneously at this function. When switched off the instrument can be zeroed no
matter what the display value. Note that the instrument keeps track of the value being zeroed at
each operation, when the total amount zeroed from repeated operations becomes greater than the
zero range value the instrument will reject the zero operation and a
ZERO RNGE Err
message will
be seen. To allow a zero operation beyond this point either the
ZERO RNGE
function value will
need to be raised or a new zero reference point introduced via the
CAL ZERO
function. If repeated
zero operations are required the
ZERO RNGE
function should be set to
OFF
or alternatively the
tARE
operation could be considered.
6.4 Zero range zero calibration
CAL ZERO
- Zero range zero calibration - a
CAL ZERO
zero operation can be used to ensure
that the display zero and the
ZERO RNGE
reference zero are at the same point after a calibration.
After a calibration the
CAL ZERO
operation can also be used to select a zero point other than
the display zero as the reference for the
ZERO RNGE
function. For example if the
CAL ZERO
operation is carried out with a display reading of
500
and a
ZERO RNGE
reading of
10
the
zero range function will allow the display to zero only if the current display reading is between
490
and
510
. To perform a calibration zero press the
^
and
v
buttons simultaneously at the
CAL ZERO
function, a live reading will be seen, press the
F
button, the message
CAL ZERO
End
should now be seen indicating that the instrument has accepted the zero point. Although the
display reading will not change as a result of the calibration zero the input value on the display at
the time of the operation will be the new zero reference point for the
ZERO RNGE
function.
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