mensor PCS 400, Руководство по эксплуатации

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7 – BI-DIRECTIONAL PRESSURE CON-
TROL
A gauge pressure instrument can be ordered for
plus and minus pressure control operation with
respect to zero gauge pressure. The plus [+] and
minus [–] keys on the keypad are used to enter a
signed control point. When in CONTROL mode the
normal increment/decrement functions of these
two keys are disabled to accommodate bi-direc-
tional operation.
Operation
Local
To enter a negative (vacuum) control point from the
front panel first press the minus [–] key and then
enter the control point. Entering a plus [+] before
a positive control point is not required, but will be
accepted. Control points in either direction must
be within the range of the minimum and maximum
control limits. All front panel displays of the meas-
ured or controlled pressure will include a preced-
ing + or – polarity sign to preclude any ambiguity.
Remote
For remote operation (GPIB or RS-232), to com-
mand a negative (vacuum) pressure the control
point must be preceded by a minus (–) sign. The
PCS 400 response will include a negative sign for
negative pressures, and the resolution will be re-
duced by one decimal place. If the resolution can’t
be reduced to accommodate the minus sign the
response will be “———”. It is not necessary to
enter a plus (+) for positive control points, and
there will not be a polarity indicator in the
PCS 400
response string for positive pressures.
NOTE:
See also External Analog Input
(Option 9), and Two’s Complement Bi-
nary Output (Option 12).
8 – PRESSURE EMULATION MODES
Mensor offers emulation mode options which allow
gauge or absolute type transducers to simulate the
other type transducer. With an emulation mode
option installed the F1 key is used in LOCAL mode
to toggle between absolute and gauge modes. When
a pressure value is displayed the suffix will change
to ‘A’ (absolute) or ‘G’ (gauge), as appropriate, to
indicate the current mode. The HELP screen will
display the full scale range and the native mode of
the primary transducer. Also, the native mode of
all of the internal transducers is recorded on the
front panel range label. In REMOTE mode the
gauge/absolute toggle is made with the command
“_PCS4 FUNC F1". With an emulation option Men-
sor can supply the user with calibration data for
both the native and the emulated modes as an
option.
The specifics of emulation mode functions, includ-
ing how long it takes to complete a change, and the
accuracy that can be attained while operating in the
emulation mode, depends on several factors in-
cluding:
a. Does the PCS 400 include an internal Baromet-
ric Reference Transducer (BRT)?
b. Are vacuum (negative) pressure readings a
requirement?
NOTE:
T h e B R T i s a n a b s o l u t e
transducer and cannot be used to emu-
late gauge pressures.
The three basic configurations for emulation
modes are explained in paragraphs 8a, 8b and 8c,
below. Some common requirements for all emula-
tion modes are:
a. All internal transducers (except the BRT in a
gauge unit) must be of the same type.
b. All transducers with full scale ranges below
15 psig must have dual differential relief
valves, and also must include a means to be
isolated from the CONTROL/MEASURE port.
PCS 400
OPTIONS
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