DayTronic IL78A, Manual

With the transducer loaded as in step  (f), adjust the Symmetry control (right above the PHASE 
control adjustment) to obtain a dead weight reading equal to that obtained in step (f).

If dead  weight  calibration  is  not  practical 

        and  the  transducer  manufacturer  has  supplied  a 

calibration  resistor  (or  resistor  value),  install  the  recommended  calibration  resistor.  See 
Fig.  5

(j)

(k)

Perfom  steps  (b)  thru  (e).  Now  activate  the  SHUNT  POSITIVE  (SHP)  terminal 
and  adjust  the  SPAN  controls  until  the  instrument  output  is  equal  to  the  Equivalent Input 
value  simulated  by  the  installed  resistor. 

Shunt  is  performed  at  zero  load.

If a negative 

Equivalent  Input

  value  is  also  provided  on  the  calibration  sheet  of  the  transducer 

under  calibration,  activate  the  SHUNT  NEGATIVE  (SHN)  terminal.  Confirm that the negative 
value can also be obtained. If necessary, adust the SYMMETRY control to obtain the negative 

Equivalent Input

 value as listed on the calibration document.  The  SYMMETRY  control  has 

approximately  7%  authority,  full  scale.

If dead  weight  calibration  is  not  practical  and  the  transducer  calibration  data  is  unknown, 
the 

Equivalent  Input

  value  for  the  factory-installed  calibration  resistor  can  be 

approximated  as  follows,  assuming  that  the  mv/v  sensitivity  rating  of  the  transducer 
and  the  bridge  resistance  are  known.

(l)

(m)

where

X

=

Equivalent Input, % of full scale

R

b

 = 

bridge resistance, ohms

K = 

transducer sensitivity, mV/V full scale

R

c

 = 

calibration resistance, ohms (59 k installed)

Sample  Calculation:  Assume  that  K  = 3.000 mV/V for a  5000-pound  load  cell 

(fullscale)  with  a  bridge  resistance  of  350  ohms.

49.4% 

of full scale = 2472 pounds

X =

25000 R

b

K R

c

X =

59000 x 3

25000 x 350

 =

ring, one unit can be designated the master, and the remaining units can be driven

from the oscillator contained in the master unit. The remaining units are designated

as slave instruments. To perform master/slave wiring, refer to Figure 4.

3.

CALIBRATION 

(cont.)

Note:  Above calculation is useful in applications involving non - star bridge shunt calibration strain gage bridges (for 
example DC bridges, and slip ring type torque sensors). Rotary transformer type sensors  which use star bridge shunt 
circuit will not equate properly and the sensor's published calibration data should be referenced. 

Calibration  IL78A.3

AC Strain Gage Conditioner

Module

IL78A