PowerTec Digimax, Инструкция по установке и эксплуатации

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Page 7
DIGIMAX
® ® ® ® ®
Manual
15 - AUXILIARY ANALOG INPUT
16 GROUND
17 + AUXILIARY ANALOG INPUT
The maximum input is +10 VDC, but the input is a differential type input, so a negative
voltage may be accepted by reversing input leads. TB2 TERMINAL 17 MUST ALWAYS BE
MORE POSITIVE (ON AN ABSOLUTE SCALE) THAN TB2 TERMINAL 15. If TB2 terminal
15 is more positive than TB2 terminal 17, the effective input will be 0.
The auxiliary analog input is for transferring an analog voltage representing a system
value (such as motor current) through the RS-422 communications link. For this type of
operation, parameter #26 must be 0. #23 is set to read out a +10 VDC input in Engineering
Units (EGU). Parameter #22 is set to low EGU, which may be zero, but doesn't have to be.
The auxiliary analog input may also be used as an analog trim or dancer (see
parameters #20 on page 19, and #26 on page 21). The input leads should be connected to
TB2 terminals 15 and 17 (not ground) and TB2 terminal 16 should be used for the shield.
If parameter #26 is 1, a 5VDC input is zero effect. Increasing voltage increases the setpoint.
If parameter #26 is 2, a 0VDC input is no effect. Increasing voltage increases the setpoint.
If parameter #26 is 3, a 0VDC input is no effect. Increasing voltage decreases the setpoint.
The maximum speed (parameter #1) may not be exceeded in speed mode.
The maximum ratio (parameter #31) may not be exceeded in slave mode.
18 RS-422 - RECEIVE
19 RS-422 + RECEIVE
20 RS-422 No connection
21 RS-422 - TRANSMIT
22 RS-422 + TRANSMIT
In order to ensure good communications, it is required that shielded cable be used in
the RS-422 communications link. The cable should have conductors no smaller than #24
AWG for distances up to 500 feet. Recommended cables are cables such as Belden
®
Wire
Company part #9829 or part #88102.
Connecting the link together consists of connecting all of the transmit terminals of the
DIGIMAX DIGIMAX DIGIMAX DIGIMAX DIGIMAX
®
units in parallel (+ to +, and - to -). Then all receive terminals are connected in
parallel (+ to +, and - to -).
ANSI standards apply to RS-422 communications. The RS-422 standard stipulates
that the number of stations shall be at least 10 without repeaters. (Repeaters are amplifiers
which strengthen the signal to feed more stations). The DIGIMAX DIGIMAX DIGIMAX DIGIMAX DIGIMAX
®
communications may
operate up to 32 units on the link.
After connecting all of the RS-422 terminals together, one end of the chain is tied to the
host (a PLC, a personal computer through an RS-422 output card or an RS-232 to RS-422
converter, or an industrial computer with an RS-422 port). Normally the "transmits" of the
DIGIMAX DIGIMAX DIGIMAX DIGIMAX DIGIMAX
®
's will tied to the "recieve" of the host, and the "receives" to the "transmits", but
check the specifications of the host to be used. The unit at the far end of the line, furthest from
the host, must have a resistor equal to the cable's impedance (120 ohms) installed across
its receive terminals. This is "terminating" the line. It prevents signal reflections from causing
spurious signals on the line. The transmit line is terminated at the host.
The RS-485 Communications standard may be used with the DIGIMAX DIGIMAX DIGIMAX DIGIMAX DIGIMAX
®
by tying the
+Transmit to the +Receive and the -Transmit to the -Receive. Terminal 20 is for the shields.
If you are putting together a large system, it is a good idea to consult someone who is
knowledgable and experienced in the art of serial communications.