c. Referring to the block diagram (fig. 7), the transducer is an LVDT (linear variable differential transformer) mounted on the
balance with the core attached to the end of the weigh-beam and the coil fixed to the mounting plate. This LVDT is of the dc-
in, dc-out variety and the excitation of 5.0 v is supplied by the J5000S Chassis. The weigh-beam is adjusted so that the output
of the LVDT at balance zero is 75 mv 25 mv. This is to prevent the output from becoming negative. The sensitivity of the
beam is adjusted to provide an output of 900 mv 100 mv for a 1 gram standard weight on the pan. The output of the LVDT is
connected to a Voltage to Frequency Converter whose output is nominally 0 to 10,000 Hz for 0 to 1 V input.
d. A radiometric measurement is made so that variations in excitation voltage do not affect the indicated value. The output of
the V/F converter is assigned to various registers which have the following modes:
(1) Z-register. Stores the output of the V/F at the zero position of the beam. With 1 gram on the pan, the contents of the
Z-register are subtracted from the output of the V/F converter and the difference is stored in the R-Z register.
(2) X-register. With any weight in the range of zero to one gram, the number in the Z-register is subtracted from the
output of the V/F converter and stored in the X-Z register.
(3) The contents of the R-Z register is shifted to the RATIO register and the ratio (shown below) is stored in the DATA
register.
(4) The contents of the DATA register are shifted to the display and on command (PRINT), to the output connector.
Previous Page
