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3.3
VOLTAGE OR TEMPERATURE DISPLAY
The Model 818 and 819 Cryopump Monitors read in voltage or temperature (kelvin, Celsius, or Fahrenheit).
To change units, press the s key or the t key or send a command over the RS-232C Serial Interface.
3.4
STANDARD CURVES
The unit stores several standard curves. Different curves may be assigned to each channel of the Model 819.
These curves, numbered 0 thru 9, are listed on the front cover of this manual as well as in Table 3-1. The front
cover also indicates the factory curve configuration of the unit. Curve 6 (DT-470 Curve 19) is the standard
curve selected unless specified differently upon ordering. Tables of voltage versus temperature for these
standard curves appear in Appendix A.
3.4.1
Curve and Alarm Action Selection
To change or check the selected curve or alarm action, use the procedure below:
1. For the Model 819, press the CHANNEL key and the s or t key until the desired channel displays.
2. Turn ON (1) DIP switch number 4 on the instrument rear marked CURVE SET.
3. Note the display now shows the number 0 or 1 on the left (alarm action) and a number between 0 and 9
on the right (standard curve).
4. To change the curve, push either the s or t key until the desired curve number displays. If a curve is not
present, it is skipped in the sequence. To select the alarm action push the LO ALARM key (0) for the
Model 818 operation or the HI ALARM key (1) for DIGI-K operation.
5. Turn OFF (0) DIP switch number 4 on the instrument rear marked CURVE SET. The instrument returns to
normal operation with the new curve and alarm action selected.
Note: A different curve can be assigned to each of the four Model 819 channels independently. However,
the alarm action applies to all four channels.
Table 3-1. Standard Curves and Alarm Temperature Limits
3.5
ALARM OPERATION
The Model 818 can set two alarm trip points (HI and LO) associated with the single sensor input. The Model
819 has four sensor inputs and two alarm trip points (HI and LO) for each input.
The deadband is ±0.025 for the setpoint less than 100 (any units) and ±0.25 for the setpoint greater than 100.
If the display is in voltage, then the deadband assumes appropriate kelvin units.
3-2
Lake Shore Model 818 / 819 Cryopump Monitor User's Manual
Curve #
Description
0
DT-500D1-8B
1
DT-500D1-8A
2
DT-5OODRC-D
3
DT-5OODRC-El
4
CTI Curve C
5
DT-500D1-8C
6
DT-470 Curve 10
7
—
8
—
9
—
Temp Range (K)
0 - 324.9
0 - 324.9
0 - 324.9
0 - 324.9
0 - 324.9
0 - 324.9
0 - 474.9
—
—
—
Operation
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