Cooper Instruments & Systems DFI 200 Hand Held Indicator User Manual

Page 10

CF 112

Version 3.1-0

Use of

and

as reference values.

Note: do not use this facility if an optional external memory chip is connected. If using the two point calibration
method (

and

) the mV/V value and scale is automatically calculated and stored at the

and

functions. After calibration using

and

the

and

values may be viewed and a

note taken of their value, ensure that you do not change either the

values whilst they are being

viewed. If the instrument is accidentally recalibrated incorrectly the

and

values recorded can be re-

entered to scale the instrument back to the same load cell. Note that the mV/V reference value stored at the

function will only match the manufacturers rated mV/V value for the load cell if

and

were

carried out at exactly 0% and 100% of rated load. For example if the manufacturer states that the load cell has a
2.000mV/V output and

and

were carried out at 0% and 50% of rated load then the

reference

value you would expect to see would be approximately half of the rated mV/V i.e. approximately 1.000 mV/V.

4.12 Calibration offset

Display:

Range: Any display value
Default Value: n/a

Allows the instrument calibration to be offset by a single point value. This value is added or subtracted across
equally the range of the instrument. This scaling method is used to correct for a constant error in the reading. The
procedure is as follows:

1. Press then release,

and

simultaneously to enter the

function. The display will show the

current display value.
2. Press the F button. The display will show

followed by the previous scale value.

3. Use the

button to alter this scale value to the required reading for the current input load.

4. Press F to accept the new scale value. The display will show

to indicate that the offset calibration

scaling has been completed.

4.13 Zero range limit

Display:

Range:

Default Value:

The zero range function is expressed as a percentage of full range (0.0 to 100.0%). The full range input is
calculated by the

figure minus the

figure for 2 point calibration or the

figure if

calibration is used. If the display value (as a percentage of range) is greater than the percentage selected in the

function then any attempt to zero the display will be aborted and a

message will be seen, the beeper will also sound repeatedly. If the zero operation is

successful then the instrument will beep once and the

message will be seen prior to the display value

going to zero.

A zero range setting of 0.0 will mean that no zero operation is possible, a zero range setting of 100.0 will mean that
the display can be zeroed at any time no matter what the display value at the time.

Example: A load cell is calibrated using 2 point calibration the

figure is 10 and the

figure is 70. If

the

function is set to 30.0 (30.0 percent) then the display can only be zeroed if the display is

below approximately 18. This is calculated by (

x 30%) i.e. (70 - 10) x 0.3 = 18.