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NI 9752 User Manual

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© National Instruments

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9

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.

Содержание NI 9752

Страница 1: ...ntroduction 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 ...

Страница 2: ...urable 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 nois...

Страница 3: ...nnections 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 wi...

Страница 4: ...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 Instr...

Страница 5: ...f 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 I...

Страница 6: ...xamples 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 configur...

Страница 7: ...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...

Страница 8: ... 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 e...

Страница 9: ...hreshold 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 us...

Страница 10: ...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 1 open 1 kΩ 5 6 k 200 Hz 33 V Measurement 2 open 1 kΩ 5 6 k 200 Hz 33 V Measurement 3 open 1 kΩ 5 6 kΩ 200 Hz 33 V Measurement 4 open 51 kΩ 0 Ω 500 Hz Active Pot 5 open 51 kΩ 0 Ω 500 Hz Active ...

Страница 11: ...r Switch 20 1 kΩ open 0 Ω 500 Hz Thermistor Switch 21 1 kΩ open 0 Ω 500 Hz Thermistor Switch 22 2 5 V 0 2 Precision Reference Table 2 Standard VR Configuration Channel VR Amplitude Voltage 1 60 VDC 2 60 VDC Table 3 Standard Hall Configuration Channel Pull up Resistor Pull down Resistor Divide Resistor Break Frequency Intended Use 1 4 7 kΩ open 0 Ω 150 kHz Hall Proximity Switch or TTL 2 4 7 kΩ open...

Страница 12: ... not exceed the 60VDC rating Product misuse can result in a hazard You can compromise the safety protection built into the product if the product is damaged in any way If the product is damaged return it to National Instruments for repair Compliance and Certifications Safety This product meets the requirements of the following standards of safety for electrical equipment for measurement control an...

Страница 13: ...ducts in an environmentally responsible manner NI recognizes that eliminating certain hazardous substances from our products is beneficial to the environment and to NI customers For additional environmental information refer to the Minimize Our Environmental Impact web page at ni com environment This page contains the environmental regulations and directives with which NI complies as well as other...

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