THE MOST COMMONLY USED BALANCE IN BIOTECH LABORATORIES IS CALLED AN ANALYTICAL BALANCE.
AN ANALYTICAL BALANCE ALLOWS US TO TAKE VERY PRECISE MEASUREMENTS, WITHIN 1 1-THOUSANTH
OF A GRAM.
THE TARE BUTTON ZEROES OUT THE BALANCE.
THE LINEARITY OF THE BALANCE BY TESTING ITS RESPONSE AT ITS MIDPOINT.
LINEARITY ERROR OCCURS WHEN A BALANCE IS PROPERLY CALIBRATED AT THE BOTTOM AND TOP OF ITS RANGE,
BUT ITS WEIGHT VALUES IN THE MIDDLE ARE NOT CORRECT.
IF A BALANCE HAS A LINEARITY ERROR BEYOND THE MANUFACTURER’S SPECIFICATIONS, THEN
IT MUST BE PROFESSIONALLY REPAIRED.
LET’S TEST OUR BALANCE.
A WOOD BLOCK, AND A CORK.
LET’S LABEL THESE ITEMS A, B, C, AND D.
AND CLOSE THE GLASS DOORS.
PRESS THE TARE BUTTON TO ZERO OUT THE WEIGH BOAT.
CLOSE THE GLASS DOORS.
THE COMBINED MASS OF ALL FOUR OBJECTS IS 99.4373 GRAMS.
THIS IS CALLED THE FULL SCALE VALUE.
RECORD THIS VALUE IN YOUR LAB NOTEBOOK.
TARE THE BALANCE AGAIN IF NECESSARY.
THE COMBINED MASS OF ITEMS A AND B IS 83.9690 GRAMS.
RECORD THIS VALUE IN YOUR LAB NOTEBOOK.
THE COMBINED MASS IS 15.4676 GRAMS.
RECORD THE VALUE IN YOUR NOTEBOOK.
THIS TOTAL IS CALLED THE WEIGHT SUM.
THEN THE WEIGHT SUM WILL EQUAL THE FULL SCALE VALUE.
ON OUR BALANCE THE TWO VALUES ARE NOT EQUAL.
LET’S TAKE THE DIFFERENCE…
99.4373 GRAMS MINUS 99.4366 GRAMS GIVES US 0.0007 GRAMS.
BECAUSE WE TOOK 2 MEASUREMENTS, LET’S DIVIDE BY 2, WHICH GIVES US 0.0004 GRAMS.
NOw WE HAVE SUCCESSFULLY IDENTIFIED THE LINEARITY ERROR AT THE BALANCE’S MIDPOINT.