SECTION 4
Rear Panel Description
A schematic of the rear panel of the Model 2002 control unit is shown in Figure 4.2 ( Rear Panel Figure). The transducer is connected to the control unit via an female
4.1 Remote Zero Input
The Model 2002 can be zeroed remotely via the I/O cable using the remote zero input line. Upon setting this line to TTL low level, the instrument will set its current pressure reading to zero. A common applica- tion of this feature is to utilize a process control output from a high vacuum gauge (for example an ion gauge controller) to automatically zero the Model 2002 whenever the pressure is below the low
4.2 Analog Output
The Model 2002 provides an analog voltage output signal (0.5 VDC linear per decade) for process control and for pressure monitoring. A plot of the analog output signal as a function of pressure is shown in Figure 4.1 . Note that the output voltage is directly proportional to the pressure over each complete decade (see detailed region in Figure 4.1) and that each decade has a different linear slope.
Above an indicated pressure of 103 Torr, the analog output signal will be +5 VDC. Below the minimal displayable pressure of 1 x
V = | (EXP + 6) | + | (MANT - 1) |
| 2 |
| 18 |
The analog output voltage is given by the following equation:
Where EXP is equal to the exponent of the displayed pressure.
EXP = -2
MANT = 1.53
V = | +(1.53 - 1) | ||
|
| 2 | 18 |
= 2 + 0.0294 
= 2.0294 VDC 
example: p = 1.53 x
EXP = +2
MANT = 9.87
V = | (+2 + 6) | +(9.87 - 1) |
| 2 | 18 |
=4 + 0.4928
=4.4928 VDC
Model 2002 page 17
