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CM73522UMC.0112
6-2. Calibration
Designed tolerance of weight measurement is +/- 1 gram. For example, if a standard
weight of 500 grams is put on the tray, the display should show a figure between ‘
499
’
and ‘501’. Otherwise, the equipment may be subject to calibration by users.
Checking accuracy of weight measurement
(1) Prepare a known weight of about 500 grams.
(2) Turn power on and, after 30 seconds stand-by, put the weight on tray.
Do not touch the equipment and table during count-down.
(3) If the display is out of ‘the known weight +/- 1’, follow the procedures below.
Calibrating the equipment for weighing accuracy
(1) Prepare a small size flat (-) tip screwdriver, 2-3 mm (1/16-1/8”) in diameter.
(2) Turn power off and remove the tray.
(3) Remove the hole plug and locate a screw in the top panel (# 7 in Section 3-1).
(4) If the measured figure was smaller than the known weight, turn the screw
clockwise (CW), by about 1/8 of a turn (45 degrees).
If the measured figure was bigger than the known weight, turn the screw counter-
clockwise (CCW), by about 1/8 of a turn (45 degrees).
* Turning it CW will increase displayed figure, and CCW will decrease display.
(5) Install the tray and follow the accuracy check procedures above.
(6) If the equipment is still out of tolerance, repeat from (2) to (5) again.
If the equipment is now in tolerance, replace the hole plug.
[Note 1] The calibration screw is a potentiometer working very sensitive. Do not turn
the screw more than a quarter turn at one cycle of calibration. The screw adjustment
should be done while the power switch is being turned off.
[Note 2] Designed tolerance of blood volume measurement of the net collected blood in
blood bag is - 0 to + 3 milliliters. For example, if the preset target volume is set at
‘500’, it’s normal that the net collected blood volume comes between 500-503 ml.
But there exist two factors that may change the result.
1) The equipment measures weight only. Blood volume is calculated from blood
weight, divided by specific gravity of blood. If the specific gravity of a donor’s
blood is different from the set figure, it will result some error (about 1-2 ml).
2) If the tubing length between clamping point and blood bag is changed, or if it is
not free, it may push or lift the tray more or less. To minimize this type of error,
the tube length should be longer than 30 cm. Refer to [Note 3] in Section 5-2.
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