Tektronix Keithley AIM6 RTD Analog Input Module User manual
RTD Analog Input Module
The AIM6 RTD Analog Input Module provides appropriate signal conditioning for either 1OOQ RTDs
or AD59O/AC2626 semiconductor temperature sensors. Four input channels are provided. All four
channels must be configured for the same type of sensor.
The AIM6 module can accept common mode voltages to rtGV Optional resistors convert current output
to voltage output for the connection of AD590 and AC2626 temperature sensors.
All connections are made to on-card screw terminals.
The AiM6 module may be piaced in siots 2 through i0 of a 500A or 5UW chassis, or siot 3 of a 575 or 576
chassis. To install the module in a 500A or 5OOP, remove the baseboard top cover and insert it into the
desired slot with the component side facing the power supply. To minimize temperature effects from
the power supply and to keep noise pickup to a minimum, it is recommended that the AIM6 module
be installed as close to the AMM module as possible. Generally, analog modules should be placed in the
low-numbered slots while digital modules should be placed in the high-numbered slots to minimize
these effects. For installation into a 575 or 576 chassis, consult the hardware manual for that chassis.
CAUTION: Always turn off the system before installing or removing modules. To minimize the possibility of EMI radiation, never operate the system with the top cover removed. Unused inputs should be connected to module ground.
User-Configured Components
One bank of screw terminals is provided on the AIM6 module. In addition to high (+>, low (-1 and
ground terminals, the AIM6 module has a single terminal to provide a +lOV excitation for AD590/
AC2626 temperature sensors. A potentiometer allows adjustment of the excitation voltage.
Table
1.
User-Configured Components on the AIM6 Module
Component Designation
-^^- .
Function
Screw terminals J164
Screw terminal E-I-
Document Number: 500-916-01 Rev. C
Input screw terminals for channels O-3, including
high, low, and ground for each channel.
Excitation terminal for strain gages and/or AD590/
AC2626 inputs.
AIMG-1
Figure 1. AIM6 Module Configuration
Connections
Terminals for the four channels available on the AIM6 are marked on the module board. A typical connection is illustrated in Figure 2. All terminals accept 16-24 gage wire, stripped to 3/16 of an inch.
CAUTION: The use of shielded cable is recommended to minimize the possibility of EM1 radiation.
E+ is a single screw terminal which provides a +lOV excitation source for AD590/AC2626 temperature
sensors connected to the AIM6 module. Information on connecting these devices to the excitation terminal is covered in the following section.
Excitation for RTDs is not provided for by this terminal, but by the signal conditioning circuitry of the
module.
Strain Gauges
AJM6-2
The AIM6 can be used to measure strain gauges. Figure 2 below details the strain gauge bridge connections.
Note: Strain gauge channels can be mixed with AD590 channels on an AlM6. However, neither strain
gauge nor AD590 channels can be mixed with RTD channels on the same AIM6. KDAC500 software
does not support engineering units conversion of strain gauge data on the AIh46. The programmer must
convert the raw voltage readings of the AMM module to engineering units.
Signal+
J164
Figure 2. AIM6 STRAIN GAUGE Connection (Channel 0 shown)
Current to Voltage Conversion
By installing optional resistors each channel can be modified to accept current input from AD590/
AC2626 temperature sensors. These resistors can be installed between the high (-I-> and low (-1 input terminals, for each channel of current input.
A 21OQ resistor is recommended for the temperature sensor inputs. The resulting voltage output is determined by Ohm’s law:
E=I*R
Voltage (volts) = Current (amps) * Resistance (ohms)
Resistance Temperature Detectors (RTDs)
The most common type of RTD is the platinum resistance thermometer, simply a coil of very pure plat-
inum wire calibrated to have a known resistance (often 1OOQ) at 0°C. This coil responds to changes in
temperature with predictable (but not linear) changes in resistance. By directing a current through the
RTD and measuring voltage, the temperature can be determined as a function of the resistance.
The wire leads that connect the RTD to the measuring device also have a resistance which changes with
temperature. This property is a potential source of measurement error, especially when the leads are
long. For this reason, RTDs are available with a third lead which minimizes the effects of the resistance
of the other leads.
AlM6-3
Connecting RTDs to the AIM6
The AIM6 module will accept both two-wire and three-wire 1OOR RTDs. An excitation current of 0.4mA
is provided automatically when the module is set to the RTD mode. While the AIM6 can accept non1OOQ RTDs (provided the resulting full scan voltage range is acceptable to the user), KDAC500 software
does not support linearization and conversion of non-100Q RTD data into degrees.
A local gain of x50 allows the RTD to measure temperatures from 200 to +7OO”C, with a voltage output
ranging from 1.629 to 5.0&W. Temperatures higher than 700 degrees should not be measured with the
AIM6 in this configuration, since at higher temperatures the voltage output of the RTD will exceed the
+5V range of the module.
RTDs of other types, with other calibrated resistances, may be connected to the AIM6 if voltage output
will be compatible with the x50 gain factor. In all cases, the output voltage (after amplification) should
not exceed rt;5V, or measurement errors will occur
When three-wire RTDs are used, the positive lead (from the single lead end of the RTD) should be connected to the positive screw terminal of the channel being measured. The negative lead from the other
end should be connected to the negative terminal, and the ground lead connected to the ground terminal (see Figure 3).
When connecting two-wire RTDs, one lead should connect to the positive terminal, and the other to the
negative terminal. Ashort jumper should be installed from the negative terminal to the ground terminal
for that channel (see Figure 4).
RTD Probe
J164
Figure 3. AIM6 3-wire Connection (Channel 0 shown)
AIM6-4