Sierra 951 Function Definitions, Flow Set Point StPt, Alarm Set Point High 1 SPH1

FUNCTION DEFINITIONS

The Mode switch (S1) cycles through the following functions.

Flow Set Point (StPt)

The Setpoint (0-5 vdc) command signal used to control the flow through a flow controller. The output voltage is 0-5 vdc. The setpoint

output is defined as:

Setpoint Output = StPt / CAL x 5.000 vdc +/- Voffset (Zero value)

Example: If the CAL value was programmed to be 7500 sccm and the desired flow rate is 5000 sccm, enter 5000 for the StPt value. Depress the ZERO switch to exit the MODE sequence and the Setpoint Output voltage will be 3.333 vdc. This is assuming the Flowmeter output had no offset voltage.

Alarm Set Point High 1 (SPH1)

SPH1 is a digital setpoint being constantly compared with the displayed reading. If the magnitude and sign of the reading�������� the SPH1 value, the SPH1 open collector output will activate and pull its respective D-Sub connector pin to ground (Ref Figure 4 on page 4). The front panel LED (H1) will also illuminate. If SPH1 is exceeded, the reading must then drop below SPH1 less the Hysteresis High (HH) value before the open collector output opens and the H1 LED turns off.

Alarm Set Point Low 1 (SPL1)

SPL1 is another digital setpoint being constantly compared with the displayed reading. If the magnitude and sign of the displayed reading��

��������� than the SPL1 value, the SPL1 open collector output will activate and LED (L1) will illuminate. If the displayed reading drops below SPL1, it must then exceed SPL1 plus the Hysteresis Low (HL) value before the open collector output opens and the L1 LED turns off.

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