Hach SIGMA 900 - Manual (Page 18)

Page 18
Auxiliary Connection 8544install.fm
Section 3
Contact Closures
The sampler controller is capable of accumulating 1 to 9999 contact closures.
Each contact closure output from a flow meter represents a specific flow
volume.
Note: The sampler provides 12 V dc
on Pin A of the Auxiliary Receptacle
and this voltage is pulsed back to
Pin C each time the contact closes
on the external flow meter. The
external flow meter must provide a
dry contact closure. Some flow meters have an adjustable output, i.e. one contact closure for
every 100, 500, 1000, 10, 000 gallons of flow, etc., while others have a fixed
output. In either case, the contact closure signal is sent more frequently for
high flow rates, and less frequently for low flow rates. The sample frequency
will increase as the flow rate increases and likewise, will decrease as the rate
of flow decreases, thus taking samples in proportion to flow rate.
To connect the sampler to a flow meter, use Signal Cable (Cat. No. 940 or
540). To connect another brand of flow meter, use the Open-ended Signal
Cable (Cat. No. 941 or 541). A contact closure input signal corresponds to
Pins A and C on the Flow Meter/Auxiliary receptacle, and signal cable
connector. The signal cable wires are white and yellow respectively. Polarity is
not important unless the same closure signal is sent to more than one
sampler.
4–20 mA Input
Note: Older model 4–20 mA
interfaces (Cat. No. 913) require
correct loop polarity to properly
work. The newer generation
(Cat. No. 2020 series) interfaces are
not sensitive to loop polarity.
An optional interface unit is available (Cat. No. 2021) which converts a
4–20 mA flow meter output into a 12 V dc pulses. At 20 mA (100% flow rate),
the interface sends ten pulses per minute; at 4 mA (0% flow rate), the
interface sends zero pulses.
The interface has a 0.9 m (3 ft) cable with connector on one end, and a 3 m
(10 ft) cable with two open wire leads on the other. Insert the connector into
the sampler receptacle labeled “AUXILIARY”, located on the left side of the
control housing. For the 3 m (10 ft) cable, the wire with clear insulation is
POSITIVE (+) and the wire with black insulation is NEGATIVE (–).
D
Liquid Level
Actuator/Auxiliary
Control Input
Black
This line is held at 5 V dc inside the sampler. When shorted to
ground (Pin B), a signal is sent to the microprocessor inside the
sampler causing it to “wake up” and begin or resume the sampling
program. It can be used in conjunction with a simple level float switch
to actuate the sampler when liquid id present or to take over after a
second sampler had finished its program. It may also be used with
any device (such as pH meter) which produces a dry contact output
to control the sampler in response to some user defined condition
(i.e. high or low pH); must be used in conjunction with Pin B
(ground).
24 V dc
(max) at
100 mA
(max)
E Special Output Red
Normally at 0 V dc, this line switches to 12 V dc upon any of the
selected event described in SECTION, PROGRAMMING.
N/A
F
Program Complete
Output
Green
Normally an open circuit, this line switches to ground for 90 seconds
at the conclusion of the sampling program. Used to “wake up”
another sampler to take over sampling or to signal an operator or
datalogger upon the completion of the sampling program.
N/A
Table 2 Auxiliary Pin Assignments
Pin Signal Description Wire Color Purpose Rating