National Instruments NI 9752 User manual

USER MANUAL
NI 9752
NI Powertrain Controls Automotive AD Combo Module
Contents
Introduction .............................................................................................................................. 2
Pinout........................................................................................................................................ 3
Hardware .................................................................................................................................. 3
Powering the Module................................................................................................................ 3
Platform Compatibility ............................................................................................................. 4
Analog Inputs ........................................................................................................................... 4
VR Sensor Inputs...................................................................................................................... 7
Hall-Effect Sensor Inputs ......................................................................................................... 9
Standard Circuit Configuration ................................................................................................ 10
Custom Configuration .............................................................................................................. 12
Physical Specifications and Characteristics ............................................................................. 12
Compliance and Certifications ................................................................................................. 12

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Introduction
The National Instruments 9752 CompactRIO AD Combo Module includes automotive-style
analog and digital inputs to interface with standard automotive sensors.
Features
• 21 Ch. Analog inputs
– 12-bit A/D Converter
– 4 ksps per channel
– Manually configurable, optional pull-up, pull-down, and divide resistors
– Anti-aliasing filter per channel
– Dedicated 2.5 V precision reference
• 2 Ch. VR sensor inputs
– 60 VDC input range
– Adaptive arming threshold
• 2 Ch. Hall-effect sensor or general purpose digital inputs
– Digital input with inverting Schmitt trigger hysteresis
– Short circuit protection
– Optional pull-up, pull-down, and divide resistors
– Analog filter for noise rejection
• Sensor power output at DB-37 connector (pins 18, 19, and 37)
– 5 V at 100 mA

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Pinout
Figure 1. Pin Assignments NI 9752
Hardware
In addition to the listed analog and digital inputs, the NI 9752 provides sensor power and ground.
The cRIO chassis backplane directly provides sensor power. Ensure that sensors do not draw
more than a total of 100 mA.
NI recommends using the NI 9923 Connector Kit for connections to the NI 9752. The NI 9923
provides proper strain relief for NI 9752 connections. Visit ni.com/info and enter Info Code
ADCOMBO for more information on parts and accessories for the NI 9752.
Powering the Module
The NI 9752 requires power from the CompactRIO backplane male high density D-SUB 15-pin
(HD15) connector, which mates with the female HD15 connector on the module. This power
source provides a regulated 5 V and ground to various digital logic and analog functions within
the NI 9752. The CompactRIO 5 V source is active whenever the CompactRIO or R Series
Expansion Chassis is properly powered. You can power the NI 9752 only at the HD15 connector
by plugging it into a CompactRIO or R Series Expansion Chassis.

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Caution Do not connect the HD15 connector to any other device. Do not connect
5 VDC power to the 5 V outputs of the DB-37 connector.
Platform Compatibility
NI Powertrain Control modules require a hardware support system to function. You cannot use
the modules independently or interfaced with third-party devices at the backplane HD15
connector. NI Powertrain Control modules are compatible with the following National
Instruments platforms:
• CompactRIO, which consists of a CompactRIO controller, chassis, or integrated
controller/chassis.
• NI PXI, which consists of any NI PXI chassis, NI PXI RT controller, and NI PXI-78xxR
R Series FPGA card. The NI Powertrain Control modules insert into an NI R Series
expansion chassis. Connect an NI R Series expansion chassis to the NI PXI FPGA card
using a SHC68-68-RDIO cable.
Note NI Powertrain Control modules are not compatible with the National
Instruments CompactDAQ chassis.
You can use NI Powertrain Control modules with NI cRIO-911x, NI cRIO-907x, and NI R Series
Expansion systems under the following conditions:
• Leave one empty chassis slot between NI Powertrain Control modules and other
NI modules.
• Maintain an ambient system operating temperature of 0 °C to 45 °C.
Note Typical specifications of National Instruments modules might not apply when
used in a system with NI Powertrain Control modules.
Note National Instruments guarantees warranted specifications for all National
Instruments modules except thermocouple modules when used in a system with
NI Powertrain Control modules.
Note National Instruments recommends the NI 9214 for thermocouple
measurements in CompactRIO systems using NI Powertrain Control modules.
Note NI Powertrain Control modules do not support Scan Interface mode,
auto-detection, or ID mode.
Analog Inputs
All analog inputs are single-ended inputs similar to production automotive ECU analog inputs
and provide filtering and over/under voltage protection.
For best results, the NI 9752 must provide the power and ground of the sensors.
The standard channel configuration provides an NI-recommended pull-up or pull-down for
every input to facilitate open/defective sensor faults.

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Standard Channel Configuration
Generic Analog Input Circuit
Figure 2 shows the generic schematic representation of all analog inputs. The NI 9752 standard
channel configuration includes a mixture of channel configurations according to the circuits
described below.
Figure 2. Unconfigured Generic Analog Input Circuit Schematic
Divided Inputs
Figure 3 shows the analog input circuit configuration for measuring voltages from 0 V to 33 V.
This is standard configuration for Channels 1 through 3 in the NI 9752. Channels with this
configuration are protected from voltage swings of ±50 V.
Figure 3. Analog Input Configuration for 0 V to 33 V Inputs

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Active Inputs / Potentiometer Inputs
Figure 4 shows the analog input circuit configuration for both active-drive analog sensors and
potentiometers for measuring voltages from 0 V to 5 V. This is the standard configuration for
Channels 4 through 16 in the NI 9752. Channels with this configuration are protected from
voltage swings of ±30 V.
This circuit utilizes a weak pull-down for open circuit detection. If the channel is connected to
a potentiometer, the pull-down slightly modifies the voltage the A/D converter receives. You
must perform a full potentiometer calibration because the voltage from this circuit does not
readily correlate to the voltage resulting from an input circuit without a pull-down.
Examples of potentiometers are throttle position and pedal position sensors.
Figure 4. Analog Input Configuration for Active Sensors and Potentiometers
Thermistor Inputs / Switch Inputs
Figure 5 shows the analog input circuit configuration for thermistors and switches to measure
voltages from 0 V to 5 V. This is standard configuration for Channels 17 through 21 in the
NI 9752. Channels with this configuration are protected from voltage swings of ±30 V.
Thermistor inputs have a strong pull-up to create a voltage divider with the sensor. Refer to the
sensor datasheet for sensor resistance curves. Most production automotive temperature sensors
are thermistors with a maximum cold resistance of approximately 100 kΩand a resistance of
approximately 100 Ωat 150 °C. The pull-up resistor of 1 kΩprovides a usable output voltage
range for thermistors of this type.
When used as a switch input, the switch must short to ground when it is closed.

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Figure 5. Analog Input Configuration for Thermistors and Switches
VR Sensor Inputs
The NI 9752 provides two identical VR sensor inputs. A VR sensor input is a standard, low-cost,
electromagnetic sensing device that contains a winding of wire around a permanent magnetic
core. The VR sensor relies on the movement of ferrous material, or steel teeth, past the tip of the
sensor to change the magnetic flux of the sensor. This movement creates a voltage pulse across
the leads of the wire coil. Figures 8 and 9 show a typical VR signal with respect to toothed
wheels, as shown in Figures 6 and 7. The VR signal is positive when a tooth approaches the
sensor tip and then rapidly swings back through zero precisely at the center of the tooth. As the
tooth moves away from the sensor tip, the voltage continues in the negative direction and then
returns to zero.
The polarity of the physical tooth or gap on the trigger wheel contributes to the polarity of the
voltage pulse from the sensor. Figure 6 demonstrates a positive physical tooth polarity and
Figure 7 demonstrates a negative physical tooth polarity. Assuming the lead polarity of a sensor
remains the same, one of the configurations generates the waveform shown in Figure 8 and the
other configuration generates the waveform shown in Figure 9.
Figure 6. Positive Tooth Trigger Wheel

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Figure 7. Negative Tooth Trigger Wheel
Figure 8. Correct Signal Polarity for VR Input Circuit
Figure 9. Incorrect Signal Polarity for VR Input Circuit
Each VR sensor input requires a positive sensor connection and a negative sensor connection.
Connect a positive sensor input to one of the NI 9752 pins labeled VR1 and VR2. Connect the
negative sensor inputs to GND pins on the NI 9752. The polarity of the sensor connection to the
NI 9752 is critical. Connect the leads of the sensor so that the positive input of the VR circuit
receives the waveform shown in Figure 8. The waveform shown Figure 9 is incorrect, and the
VR circuit does not properly respond to this waveform. The rapid zero crossing of the VR signal
must be in the negative direction.
The physical center of each tooth or gap corresponds to a known angular position of the trigger
wheel. This physical center of the tooth or gap always corresponds to the rapid zero-crossing of
the generated voltage pulse.

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The rapid negative zero-crossing of the raw sensor signal corresponds to the rising edge of a
digital pulse sent to the RIO FPGA. The VR output signal to the FPGA becomes TRUE at the
rapid negative zero crossing of the external VR pulse and remains TRUE until the external VR
pulse returns to 0 V shown in Figure 10. Within LabVIEW FPGA, the system designer can route
this digital signal to the EPT CrankSig input, EPT CamSig input, or any other speed
measurement subVI.
Figure 10. VR Input Pulse and Resulting Digital Output from VR circuit
The absolute maximum VR pulse amplitude the circuit allows is 60 VDC. If the input signal
exceeds this voltage, damage might occur to the circuit. The amplitude must not exceed 60 VDC
at maximum engine speed. The minimum VR pulse amplitude that generates a digital output by
the VR circuit is ±200 mV.
The VR circuit implements adaptive noise rejection features during continuous incoming VR
pulses. In general, an adaptive arming threshold voltage is generated with each VR pulse and
bleeds down thereafter. The next pulse must have an amplitude that exceeds the arming threshold
for a digital output to be generated at the rapid zero-crossing. The initial arming threshold is set
to approximately 70% of the amplitude of each pulse.
Given a constant gap between the sensor and the trigger teeth, the amplitude of a VR pulse is
directly proportional to the speed of the trigger wheel. For example, if the VR amplitude at
1000 RPM is ±10 V, the amplitude at 2000 RPM is ±20 V. By using an oscilloscope to measure
the VR amplitude at a low speed, you can use this relationship to determine the maximum
amplitude at the maximum speed. If the maximum amplitude of 60 VDC will be exceeded at
maximum speed, you must increase the sensor gap or obtain a custom VR circuit configuration
from NI.
Hall-Effect Sensor Inputs
The NI 9752 includes two identical Hall-effect sensor input circuits. The Hall-effect inputs take
a digital input from a Hall-effect or proximity sensor. Typical sensors include an open-collector
output that requires a pull-up resistor at the collector. The Hall-effect inputs read active TTL
compatible signals. The standard configuration includes a 4.7 k pull-up to 5 V for use with
open-collector-type inputs. The input is protected against typical automotive battery voltages
and can be connected to actively-driven battery voltage signals. Channels with this configuration
are protected from voltage swings of ±30 V.

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The circuit output to the RIO FPGA reverses the polarity of the input by going low when the
input voltage is greater than 2.0 V. The output goes high when the input is less than 1.0 V.
Figure 11 shows the standard configuration of the Hall-effect sensor input circuits.
Figure 11. Hall-Effect Circuit Input Configuration
Standard Circuit Configuration
The NI 9752 comes with a standard configuration as illustrated in Table 1 below.
Table 1. Standard Analog Configuration
Channel
Pull-up
Resistor
Pull-down
Resistor
Divide
Resistor
Break
Frequency Intended Use
1open 1 kΩ5.6 k 200 Hz 33 V Measurement
2open 1 kΩ5.6 k 200 Hz 33 V Measurement
3open 1 kΩ5.6 kΩ200 Hz 33 V Measurement
4open 51 kΩ0 Ω500 Hz Active/Pot
5open 51 kΩ0 Ω500 Hz Active/Pot
6open 51 kΩ0 Ω500 Hz Active/Pot
7open 51 kΩ0 Ω500 Hz Active/Pot
8open 51 kΩ0 Ω500 Hz Active/Pot
9open 51 kΩ0 Ω500 Hz Active/Pot
10 open 51 kΩ0 Ω500 Hz Active/Pot