Yokogawa AC8 Calibration Units - Manual (Page 6)

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IM 11M6D2-02E-A
IV. WIRING
4.1 Wiring the AC4/AC8 to the AV550G Averaging unit
Please refer to appendix A for the system configuration
drawing.
Solenoid, Relay and Pressure Switch wiring connections
The AC4/AC8 uses 120VAC, 60 Hz for all solenoids. Al-
though two internal 1 amp fuses are provided for the ±120
VAC terminal, an external 5 amp circuit breaker is recom-
mended. Included with each fuse is an LED that is activated
when the fuse is blown. Recommended wiring is 14AWG,
run in conduit. If conduit is not used, wiring should have a
suitable jacket to meet environmental and regulatory codes.
The AC4 unit requires a maximum of 8 conductors, whereas
the AC8 requires 12 conductors.
NOTE
A 120 VAC relay (included with NEMA 4 enclosure), shown at ter-
minal K1, is required at the AV550G if a pressure switch is used.
This prevents noise caused by a low voltage pressure switch
signal from being run in the same cable as the 120 VAC solenoid
signal.
The relay is prewired as NORMALLY CLOSED (NC) to
contact input #1 at the control card (terminal 7 and 9) of the
AV550G.
Figure 4.1 AV550G Input Contact Screen
WARNING
When the relay is deactivated, the unit will not calibrate. The
relay remains closed unless a 120 VAC source is connected to
energize it. Terminal 7 of the relay provides 120 VAC. Neutral
voltage is connected to terminal 2 of the relay from the AC4/AC8
calibration unit.
The relay switch is designed to OPEN when energized as
depicted in the flow diagram shown in Figure 4.2. A pressure
switch input completes the 120 VAC signal used to energize
the relay, which is wired at the calibration unit as Normally
Open (NO), where Open = Low or Zero tank pressure. The
AC4/AC8 unit is prewired with the jumper in place, so that
the relay will be energized and OPEN. However, if the pres-
sure switch input is used, then remove the jumper between
the terminals labeled PS at the calibration unit’s terminal
strip, and attach the pressure switch. The pressure switch is
wired as normally open.
Pressure
Switch
Relay
Calibration
Status
Cal Gas
Pressure
OK ?
Relay Deenergized
and
CLOS ED
Pressure Switch
OPEN
Relay Energized a nd
OPEN
Pressure Switch
CLOS ED
CALIBRATE
YES
NO
STAR T
DO NOT
CALIBRATE
Pressure Switch U sed a s Input to R elay
Calibration
Using
Pressure Switch AND Relay
Figure 4.2: Calibration Using Pressure Switch and Relay Flow
Chart
The recommended pressure switch configuration is to the
high pressure side of the zero gas regulator. This is preferred
because it gives the earliest warning of a decrease in zero
gas pressure. The switch is threaded into the high pres-
sure purge port of the dual stage regulator on the zero gas
cylinder.
4.2 Pressure Switch, M1133AR, Set Point Procedure
For the AC4/AC8 Autocal units, a gas pressure set point is
used to indicate that the calibration gas (zero gas) is low.
Pressure Switch M1133AR is a cylindrical style pressure
switch which uses a diaphragm or piston sensor to detect a
pressure change. The recommended set point is 200 psi on
the fall. At the predetermined set point, a SPST switch actu-
ates, converting a pressure signal into an electrical signal.
Figure 4.3: Pressure Switch and Dual Stage Regulator
The following procedure is required to adjust the set point:
1. Thread the pressure switch into the high pressure gauge
port on the regulator.
2. With power disconnected, slide the cover on the switch
toward the electrical termination while twisting it to over-
come friction.
3. Connect the power to the terminal or leads.
4. Insert a flat head screwdriver (1/8”) into the adjustment
slot and turn counterclockwise to increase the setting or
clockwise to decrease the setting.
M1133AR
Pressure Switch
M1132ZX Dual
Stage Regulator