Lake Shore Model 218 Temperature Monitor User’s Manual
Introduction
1-3
1.1 MODEL
218
FEATURES
PTC Resistor Measurements
The Model 218 can read up to eight 100
Ω
, 1000
Ω
PTC (positive temperature coefficient) or any
other PTC resistive sensors using their standard curves or individual calibrations. Platinum RTDs are
known for their wide range of operation and uniform sensitivity. The Model 218 can read Platinum
RTDs to achieve temperature readings greater than 1000 K (727 °C). Platinum RTDs sold by Lake
Shore are limited to 800 K (527 °C).
Diode Measurements
The Model 218 can read up to eight Lake Shore DT-470 or any other diode temperature sensor.
Diode sensors are easily interchangeable and provide a wide measurement range from 1.4 to 475 K.
Many diodes like the DT-470 follow a standard temperature response curve that may eliminate the
need for costly or time consuming individual calibration. The convenient SoftCal™ feature can be
used to improve the accuracy of less expensive DT-470 sensors.
NTC Resistor Measurements
The Model 218 can read up to eight NTC (negative temperature coefficient) resistor sensors using
their standard curves or individual calibrations. NTC resistor sensors are typically used in specialized
applications such as magnetic and radiation environments. In some applications, the constant current
excitation of the 218 may limit the useful range of NTC resistor sensors (refer to Table 1-2).
Configurable Sensor Inputs
The Model 218 has eight constant current sources (one for each input) that can be configured for a
variety of sensors. The inputs can be configured from the front panel or via computer interface and
are grouped in two sets of four. Each set of four inputs are configured for the same sensor type (i.e.
all 100
Ω
Platinum or all Silicon Diodes, etc.).
Sensor Input Reading Capability
The Model 218 has two high resolution A/D converters to increase its update rate. It can read sensor
inputs more quickly than other scanning monitors because it does not have to wait for current source
switching. The result is 16 new readings per second allowing all inputs to be read twice each second.
Inputs can be turned off to obtain a higher reading rate on fewer sensors. All readings can be read
out of the instrument with the IEEE-488 interface. The serial interface can also be used to read all
readings if it is operated efficiently. The display is updated twice each second.
Temperature Response Curves
The Model 218 has standard temperature sensor response curves for silicon diodes and platinum
RTDs. It can support a wide variety of temperature sensors that do not have a standard curve
because a unique 200 point user curve can be stored for each of the eight inputs. CalCurves™ for
Lake Shore calibrated sensors can be stored as user curves. User curves can be entered from the
front panel or with a computer interface. The built in SoftCal™ algorithm can also be used to generate
improved curves for DT-470 diodes and platinum RTDs that are stored as user curves.
Configurable Display
The eight display locations on the Model 218 are user configurable. These locations can be used to
display a single readout for each of the eight inputs or for more than one readout for fewer inputs.
Sources for readout data are temperature units, sensor units and results of the math function. Input
number and data source are always displayed for convenience.
Summary of Contents for 218S
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