Hardy HI 2151/30WC Single-Scale Controller - Manual (Page 107)

Chapter 7 - Operation
7-9
RS-422/485
Electrical
Specifications Description Specification
Receiver Impedance 12 k ohm
Description Specification
Receiver Common Mode Range +12 to -7 V
Maximum Input Threshold +200 mv
Minimum Input Hysteresis 50 mv
Driver Output Capability +60 ma at 2 V differential
Driver Short Circuit Limit 250 ma to +12 or -7 V
Bus Loading By Unpowered Board One Receiver Load
Instrument Serial
Communications
About Instrument
Serial
Communications The HI 2151/30WC's serial options provide the user with a full comple-
ment of RS-232C, RS-422, and RS-485 communications. There is a
standard RS-232C/422/485 serial port on the main board. Each port can
be an output only port to drive a printer or similar device, or as a bi-
directional port for both status and control.
Printer Output Below is an example of the printout with the weight controller format-
ted for Gross, Net and Tare.
>
GROSS
1.430 LB
NET 0.430 LB
TARE 1.000 LB
Serial Protocol -
Multidrop Mode
About Serial
Protocol Multidrop
Mode Hardy Instruments HI 2151/30 WC weight controller employs an
ASCII command protocol and accompanying command set, described
in the following paragraphs. The protocol is via RS-232 or RS-422 with
the network being called Hardy Link. Hardy Link supports a multidrop
configuration.
• Serial Protocol - Multidrop Mode
Multidrop is a configuration denoting that there are multiple
HI 2151/30WC units connected to a host computer whereby
each HI 2151/30WC receives and sends data through a
unique address. The fastest possible instrument response
will be from the multidrop configuration. The multidrop
configuration also lends itself well to host computer control
of multiple weight controllers. RS-422/485 is utilized and
provides excellent noise immunity and drive capability sup-
porting long cable runs.