Before Mounting; Compensation Value; Compensation Value Setting - Sony BS78 Series Instruction Manual

2-3. Before Mounting

2-3-1. Compensation Value

of the scale is approximately 0.55 µm/22 µinch, while the detector signal
The hologram grating pitch P
G
is theoretically 1/4 of this, that is 0.14 µm/5.5 µinch. This value differs slightly from scale to scale.
pitch P
S
Therefore, it is necessary to additionally make the pitch compensation for each scale, in order to detect
precise displacements.
= 0.1379[|] [|] [|] [|] µm at 20 dC/
The lowest four digits of the detector signal pitch for each scale P
S
68 dF show the compensation value.
Before operation, be sure to always set the compensation value of the scale for the detector when using a
detector that allows input of compensation values.
Linear compensation must be performed using the customer's machine if the compensation value cannot be
set.
When you operate the unit in an environment where the temperature is not 20 d d d d d C/68 d d d d d F
To operate the unit in an environment where the temperature is not 20 dC/68 dF, adjust the compensation
value as shown below to make a temperature adjustment. The following example shows the adjustment
method for an operating temperature of 23 dC/73 dF.
Example : The compensation value shown on the compensation value label is [1] [2] [3] [4].
0.1379 [1] [2] [3] [4] x {1 + (23_20) x (_0.7 x 10 )} = 0.1379 [1] [2] [0] [5]
_6
Temperature difference from 20 dC/68 dF
Coefficient of thermal expansion of the scale (See page 18.)
The compensation value after temperature adjustment will be [1] [2] [0] [5]. Set the detector to this value.

2-3-2. Compensation Value Setting

See the section "Compensation Value Setting" of the detector (BD60/95 series) instruction manual.
n
The compensation value of the detector (BD60 series) is set to all zeros at the time of shipment. In this state,
the alarm sounds and you cannot operate the unit. Be sure to set the detector to the correct compensation
value of the scale before operation.
In addition, the resolution must be calculated for detectors that do not perform compensation, so refer to the
detector instruction manual.
BS78
4
(E)