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dc571af
DEMO MANUAL DC571A
HARDWARE SETUP
JUMPERS
JP1:
Select the connection for the common pin, either
ground or external connection. Single-ended measure-
ments are taken with respect to this pin.
JP2 and JP3:
Select the source for differential reference.
Selecting 5V and GND will use the onboard 5V reference.
Select EXT to use an external reference.
JP5:
Select notch frequency, 60Hz or 50Hz. Alternatively,
this jumper may be removed and an external conversion
clock applied to the center pin of JP5.
CONNECTION TO DC590 SERIAL CONTROLLER
J1 is the power and digital interface connector. Connect
to DC590 serial controller with supplied 14-conductor
ribbon cable.
ANALOG CONNECTIONS
Analog signal connections are made via the turret posts
along the edge of the board (CH0 to CH15.) Also, if you are
connecting the board to an existing circuit, make full use
of the four ground connections at the corners of the board.
EXPERIMENTS
Figure 2 shows a number of applications for the LTC2418.
CH0, CH1, CH2
Channels 0 and 1 measure the differential output of an
Intersema MS5401 absolute pressure sensor. The 6.8k
resistor performs a first order temperature compensation
of the bridge output. CH2 measures the bridge voltage,
which provides a convenient temperature measurement.
This can also be used to perform further temperature
compensation in software.
CH3
Channel 3 measures the output of a thermistor in a half
bridge circuit. Many thermistors will work, the constraints
are that the bridge output must have an impedance of
less than 20k and the voltage must not go above V
REF
/2.
CH4
Channel 4 measures the output of a type J thermocouple.
The circuit shown for channel 3 can be used for cold junc-
tion compensation. The cold junction sensor should be
close to the connections of the thermocouple to the board.
CH5
Channel 5 measures the output of an Omega OS36-01
infrared thermocouple. This can be used for remote tem-
perature measurement.
CH6
Channel 6 measures the photocurrent of a Hamamatsu
S1336-5BK photodiode.
CH7
Channel 7 measures the output of a resistive attenuator.
CH8, CH9
Channels 8 and 9 measure the drop across a Deltec SWE-
3000-50 current shunt. Up to 3000A can be measured,
with a resolution of 60mA. With careful grounding, both
positive and negative currents can be measured. Care
must be taken to ensure that both inputs stay more posi-
tive than GND–0.3V.
CH10
Channel 10 is buffered with an LT1793 FET input amplifier
suitable for very high source impedance measurements.
CH11
Channel 11 measures the output of a precision rectifier.
CH12, CH13
Channels 12 and 13 measure a 3-wire RTD. The differential
voltage is the output, and CH12 single-ended reading is
the ground lead compensation.
CH14, CH15
Channels 14 and 15 measure the output of a 350Ω bridge.
This is standard for a wide variety of sensors. Typically
the full-scale output voltage is only 10mV. However, the
LTC2418 still gives 13 effective bits of resolution with no
amplification.
