Hitachi HSC-2100 Hardware Manual page 14

(chapter 4, page 4-9)
When wiring a pulse counter module, be sure to wire it with a shielded twisted-
pair cable and ground the cable by Class D grounding.
The shielded twisted-pair cable must be laid at least 30 centimeters away from
noise sources, such as power cables and input/output cables. Never lay it in
parallel with those noise sources, and the length of the cable laid must be
shortest possible.
If a counting error occurs in the pulse counter module that has been wired
according to the above rules, lay the shielded twisted-pair cable in a dedicated
duct or conduit, and then ground the duct or conduit.
Any input terminals that need not be used must be wired as follows:
• If the pulse counter module is used with one-phase pulse input, short the two
input terminals of each of the two pairs of two-phase pulse input terminals;
that is, short A1S and A1C together, then short B1S and B1C together, and
then ground them all together.
• If it is used with two-phase pulse input, short the one-phase pulse input
terminals A2S and A2C together and then ground them together.
• If the stop-signal input terminals STOPS and STOPC need not be used, short
them together and then ground them together.
A pulse generator may be connected to the pulse counter module by using
either voltage-transistor connection or no-voltage-transistor connection (see
below). Voltage-transistor connection should be used when grounding is
made on the pulse generator side. No-voltage-transistor connection should
be used when grounding is made on the pulse counter module side.
Do not connect a contact to any pulse input terminal. Disregarding this rule
may result in counting errors due to contact bouncing during closing and
opening of the contact.
Voltage-transistor connection
S
C
Voltage-contact connection (prohibited)
S
C
Pulse counter module
Pulse counter module
NOTICE
No-voltage-transistor connection
S-11
Pulse counter module
S
C