Operation; Input Selection; Displaying Option Readings; Curve Selection - Lakeshore 340 User Manual

10.5.3 Operation

10.5.3.1 Input Selection

After Model 3465 option installation, front panel operation allows configuration of input C assigned to the
capacitance input. Without the option, only A and B inputs are available. For an example of option input
selection, press Input Setup to display the INPUT SETUP screen. Use the s or t key to select inputs A, B,
or C . Select C and press Enter to display available settings for the option.

10.5.3.2 Displaying Option Readings

Readings from option input C display in sensor units, nanofarads (nF). To add an input reading to the display,
press Display Format.

10.5.3.3 Curve Selection

The Model 340 with a 3465 option does not support temperature conversion so no temperature response
curves can be selected. Any feature of the Model 340 that requires temperature to operate is not supported
with the 3465 option. Selecting temperature units results in a NO CURVE message or display 0K.

10.5.3.4 Range Selection

The Model 3465 option input has two input voltage ranges, 15 nF and 150 nF. The lower range is specified to
15 nF, but can read up to 25 nF, and is recommended for CS-401 series sensors. The higher range, is
specified to 150 nF, but can read up to 250 nF, and is recommended for CS-510 series sensors. To select an
input range, press Input Type.

10.5.3.5 Temperature Coefficient

Capacitance sensors can have both a positive and negative temperature coefficient (slope). They have a
positive temperature coefficient at very low temperatures and a negative temperature coefficient at warmer
temperature. Sensor data sheets detail where the coefficient changes. There is often a temperature range
where the sensor is not usable.
Temperature control is impossible if the Model 340 does not know which slope the sensor is on. System
overheating can result if the wrong coefficient is chosen. The user must select a temperature coefficient
before control is switched to the 3465 input. To select a temperature coefficient, press Input Type.

10.5.3.6 Control Channel Changes

The 3465 option continues control at a stable temperature established with another sensor. Allow temperature
to stabilize for one hour after large temperature changes to allow capacitance sensor recovery.
When the control channel is changed to the capacitance input, the Model 340 changes the control setpoint to
the present capacitance reading. It is not necessary for the user to write down the capacitance value and
enter a new setpoint. Control parameters, P and I, may need to be changed for stable control. To change
control channel, press Control Channel.

10.5.4 Computer Interface Commands

Most of the computer interface commands used by the Model 340 are independent of installed options or
sensor type. The following commands or formats change when the 3465 is installed.
1. In command strings the <input> field accepts A, B or C instead of only A and B.
2. The INTYPE command changes to the following format. The TYPE? query changes accordingly.
INTYPE <input>,,,<coefficient>,,<range>
<input>: Specifies input to configure: C .
<coefficient>: Temperature coefficient: 1 = negative, 2 = positive.
<range>: Input range: 0 = 15pF, 1 = 150 pF.

10.5.5 Specifications

The 3465 Option Card input specifications are listed in Table 1-2.
Options and Accessories
Lake Shore Model 340 Temperature Controller User's Manual
<excitation>: 0
<type>: 11 - Capacitance
<units>: 3 (nanofarads)
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