APPENDIX
– Selection and Mounting of Encoder
191
Figure 60: Encoder with a capacitor
(common to ground)
Figure 61: Encoder with no capacitor
(common to ground)
Exceeding Operating Specification
Do not exceed the operating specification of
the encoder/drive, in order to prevent the
encoder from providing incorrect data.
All encoders have inherent mechanical and
electronic limitations regarding speed. The
combination of several design factors including
bearings, frequency response of the
electronics, and PPR of the encoder, etc.
combine to determine "maximum operating
speed". Exceeding the maximum speed may
result in incorrect data or premature failure.
Both the electrical and mechanical encoder
specifications can be provided by the encoder
manufacturer.
To determine the encoder's maximum
operating speed:
Step 1: Determine maximum electronic
operating speed in RPM.
PPR
Encoder
60
x
(kHz)
response
freq.
Encoder
RPM
Step 2:
A. If the RPM calculated in Step 1 is less than
or equal to the encoder's maximum
mechanical RPM specification, then the
RPM calculated in Step 1 is the maximum
operating speed specification for this
particular encoder application.
B. If the RPM calculated in Step 1 is greater
than the encoder's maximum mechanical
RPM specification, then the maximum
mechanical RPM specification is the
maximum operating speed for this encoder
application.
Step 3:
Compare the maximum operating speed as
determined in Step 2 above with the
application requirements.
To determine if the application exceeds the
operating specification of the HPV 900 Series
2:
Calculate the maximum pulses per
revolution (PPR) for this application (using
the HPV 900 Series 2 frequency limit of
300 kH
z and 120% of the application’s top
speed)
2
.
1
max
RPM
n
applicatio
max
60
x
Hz
300,000
PPR
Verify that the selected encoder’s PPR is
below the calculated maximum PPR
(PPRmax) for this application
Encoder Supply Voltage
Ensure proper encoder supply voltage
and use highest possible voltage available, in
order to ensure proper operation and increase
noise immunity
Ensure that the voltage drop of the encoder
wiring is such that the minimum power supply
voltage for operating the encoder is not
violated. (i.e. 5VDC
5% power supply and
5VDC
10% encoder specification is violated
when the encoder draws 0.3 A and it is wired
with 500 ft at 22 AWG)
Use an encoder with an internal supply
regulator
Use a wide supply range encoder
(i.e. 5
– 15 VDC)
It is also preferred that the encoder be
powered by the HPV 900 Series 2’s 12VDC
power supply in order to help with noise
immunity by having the signals at a higher
voltage level.
