CPL490

USER’S GUIDE for the

CPL490

Wide Bandwidth Picometer Capacitive Displacement Sensor

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TABLE OF CONTENTS

• Approvals and Safety Considerations
  • Probe Tip Contact Caution
• Helpful Technical Support Documents Online
• CPL490 Wide Bandwidth Picometer Capacitive Displacement Sensor
  • Description
  • Basic Operation
  • Making a Basic Measurement
  • Interpreting the Output Voltage
  • Overview of Front Panel Controls, Indicators, and Connectors
    • Zero Adjust
    • Calibrated Range Indicator (Near Far)
    • Analog Output
    • Ground
    • Probe Connector
• Multiple Channel Measurements
• Specifications
• Changing CPL190/290/490 Bandwidth Settings
• Elite Series Enclosures
  • Power Specifications
  • EN191, EN192, EN193 Power Connector
  • External Power Supply
  • DAQ Connector Pinout
  • Mechanical Specifications: EN191, EN192, EN193
  • Mechanical Specifications: EN196, EN198
• Accessories
  • Air-Bearing C-LVDT: Capacitive LVDT-Type Contact Sensor

Approvals and Safety Considerations

The Elite Series is compliant with the following CE standards:

Safety: EN 61010-1:2010

EMC: IEC 61326-1:2013, IEC 61326-2-3:2013

To maintain compliance with these standards, the following operating conditions must be maintained:

• All I/O connecting cables must be shielded and less than three meters in length
• AC power cables must be rated at a minimum of 250 V and 5 A
• AC power must be connected to a grounded mains outlet rated less than 20A
• Use the included CE approved power supply with 1-, 2-, and 3- slot enclosures. If an alternative power supply is used, it must have equivalent CE certification and provide safety isolation from the mains according to IEC60950 or 61010.
• Sensors must not be attached to parts operating at hazardous voltages in excess of 33VRMS or 70VDC

Use of the equipment in any other manner may impair its safety and EMI protections.

Probe Tip Contact Caution

The sensing tips of capacitive probes produce voltages as high as 70 Vrms. These are high frequency voltages with very low power so they pose no danger. Normally when the probe tip is touched, the probe stops functioning and voltage is reduced to near zero. But under certain circumstances, the voltage may cause a slight tingle or burning sensation, especially with the second generation probes used with the CPL490. For maximum performance probe tips should remain free of oils or other contaminants.

For these reasons, it is recommended the probe tips not be touched.

Helpful Technical Support Document Online

Lion Precision’s web site has a large selection of technical documents (TechNotes and Application Notes) in the Technical Library. These documents provide detailed descriptions of the operation and use of Lion Precision high-performance sensors.

The Technical Library can be accessed at: www.lionprecision.com/technical-library/

Some of the titles include:

• Understanding Sensor Resolution Specifications and Effects on Performance
• Capacitive Sensor Theory of Operation
• Error Sources: Probe/Target Angle
• Capacitive Sensors in Vacuum
• Capacitive Sensor Phasing and Ungrounded Targets
• Capacitive Probe Cabling Considerations
• Elite Series Phase/Amplitude Frequency Response
• Z-Height Measurement with Capacitive and Eddy-Current Sensors
• Thickness Measurement with Capacitive Sensors
• Glue Sensing with Capacitive Sensors

Description

The CPL490 Capacitive Sensor is a very high precision, noncontact measurement device. The output voltage changes in linear proportion to changes in the gap between the probe and the target. The sensor is normally used to measure conductive targets, but it can also be used with nonconductive targets in some applications. For more information about measuring nonconductors, visit the Technical Library at www.lionprecision.com or call for assistance.

The CPL490 only works with 2nd Generation Probes which include integral electronics.

Basic Operation

The output voltage is accessed via the front panel BNC connector, or by a data acquisition system via the high-density connector on the rear of the enclosure. This connector can connect directly to many National Instruments™ data acquisition products. See the enclosure section of this manual for specifics on the system DAQ connector (page 19).

As the gap between the probe and target changes, the output voltage will change accordingly. As the probe approaches the target, the output voltage will become more positive.

Note: “Near” and “Far” lights (red) indicate that the probe is out of its calibrated range and the output is not guaranteed to be accurate even though the voltage may continue to change.

Probes are calibrated to specific modules. With multiple channel systems, be sure the number on the probe cable (near the connector) matches the number on the module handle. Calibration detail is provided on calibration sheets shipped with the product.

Noncontact sensors normally measure changes from a reference position.

Making a Basic Measurement

1. Connect probe to module
2. Set the target to a reference position or condition
3. Mount probe near target (probes should be mounted by the 8 mm diameter probe body which extends from the larger probe electronics housing)
4. Adjust the probe position until the Near/Far indicator is at center position
5. Use the Zero adjustments to adjust the output voltage to zero (optional)
6. As the probe/target gap changes, the output voltage will change accordingly

Interpreting the Output Voltage

The amount of change of the output voltage for a given change in the probe/target gap is called Sensitivity. The sensitivity of the sensor is listed on the calibration sheets which arrived with the sensor.

Change in gap calculation:

Gap Change = Voltage Change / Sensitivity

For example: With a sensitivity of 1 V/2 μm and a voltage change of 3 V, the gap change would be 6 μm (3/0.5).

Overview of Front Panel Controls, Indicators and Connectors

Zero Adjust

Provides a DC shift of the analog output voltage after the probe is initially positioned. The adjustment has a range of ±1 VDC. Typically, the analog output voltage is adjusted to zero volts at range center. When the Zero switch is in the off position, the zero adjustment has no effect.

Calibrated Range Indicator (Near Far)

Indicates where the probe is within its calibrated range. Green LEDs indicate that the probe is in its calibrated range and the output voltage is an accurate representation of the target position. Red LEDs indicate that the probe is out of range. When the probe is out of range, the output voltage may not be an accurate indication of the target position even if it is still within the ±10 VDC range. The Zero adjust has no effect on the Calibrated Range Indicator.

Analog Output

Provides connection to the analog output voltage, which is linearly proportional to the distance between the probe and the surface of the object being measured. A typical output voltage range is ±10 VDC. The specific range is listed on the calibration sheet shipped with the device.

The analog output provided on the data acquisition (DAQ) connector on the rear of the enclosure is differential. See the enclosure section of this manual for specifics on the system DAQ connector (page 19).

Ground

A banana-plug cable can be connected here for grounding the target. In most cases, separate grounding of the target is not necessary. If the target is not grounded through another path, and the output exhibits excessive electrical noise, grounding the target may reduce the output noise. When low-noise operation is critical, separate grounding is recommended even if the target is well grounded through another path.

Probe Connector

Connect the probe by aligning the red dots on the connectors and inserting the probe connector.

To disconnect the probe, pull on the knurled barrel of the probe connector to release it. DO NOT PULL ON THE CABLE.

Multiple Channel Measurements

Using multiple sensors on the same target requires that the sensor excitation voltages be appropriately selected. Systems ordered for multiple channel use on the same target will be specially calibrated to avoid inter-channel interference. Using multiple CPL490s together which are not so calibrated may produce interference in the output voltages of all channels. Sensors that will be used together to measure the same object must be ordered together so they can be appropriately calibrated. Using multiple sensors not so calibrated may not provide accurate results.

Specifications

These specifications are typical for standard components and calibrations. Customizations can affect performance. Check the calibration sheet shipped with the product for specific details on your system.

In high EMI environments (10 V/m), output noise may rise to 0.5 VRMS and DC value may shift 0.7 VDC.

Changing CPL190/290/490 Bandwidth Settings

The CPL190/290/490 provides a two-position DIP switch for setting bandwidth.

When changing bandwidth, change all modules in the system. Bandwidth is a system-wide setting; bandwidth switches on the modules within a system are interconnected.

All of the bandwidth switches must be in the same position for predictable results.

This switch is located as shown in the drawings at the right. The following table shows the bandwidths available and their associated dip switch settings.

Bandwidths listed are approximate. Actual values depend on the probe and calibration.

Bandwidth DIP Switch Access

Be careful to only change switches and jumpers as directed in this manual. Any other changes will affect the calibration of the module.

Elite Series Enclosures

Elite Series enclosures provide housing and critical signals to Elite Series modules. Sensor output signals are available via a rear-panel high-density connector which is configured for direct connection to National Instruments™ data acquisition hardware.

The specific Elite Series enclosure model number indicates the maximum number of slots available for plug-in modules as well as other features:

Power Specifications

EN191, EN192, EN193 Power Connector

External Power Supply

EN191, EN192, and EN193 systems include an external power supply. The supply has a connector which allows direct connection to the enclosure.

This supply features a high-frequency (100kHz) switching supply. The high switching frequency allows the sensing modules to operate at maximum resolution.

DAQ Connector Pinout

All unlisted pins are reserved for proprietary use by Lion Precision and should not be connected to external contacts.

Mechanical Specifications: EN191, EN192, EN193

Mechanical Specifications: EN196, EN198

ACCESSORIES: Air-Bearing C-LVDT: Capacitive LVDT-Type Contact Sensor

The Air-Bearing C-LVDT converts a capacitive sensor using a standard capacitive probe into a high-precision contact displacement sensor similar to an LVDT. The capacitive probe is installed in the top of the C-LVDT body where it measures the location of a target connected on the inside end of the stylus. The C-LVDT uses a linear air-bearing for nearly frictionfree movement of the stylus, and the porous carbon air bearing is square to prevent stylus rotation. Adjustable air pressure for extending the stylus provides for contact forces less than one gram, and the C-LVDT features a retraction port through which application of air pressure will retract the stylus.

The C-LVDT uses an interchangeable diamond tip. Diamond has been selected over ruby for the following reasons:

• Low Friction – Side forces cause less lateral deflection from moving targets and less hysteresis on direction reversal.
• Highly Polished Surface – Diamond accepts and holds a high polish, minimizing the possibility of scratching the measured surface.
• Minimal Wear – Increased accuracy and longer life.

Contact Force Adjustment
There is a contact force adjustment screw located on the end of the probe body near the cable exit. Use a 1/16″ hex key to turn the adjustment clockwise to increase the contact force or counter clockwise to decrease it. Contact force is also a function of the air pressure applied to the C-LVDT. To maintain constant contact force, supplied air pressure must be held constant.

Air Exhaust

The 0.1″ slot around the body near the top of the C-LVDT is where air is exhausted. Do not clamp the C-LVDT over this ring. The ring must remain at least partially clear at all times for proper operation of the C-LVDT.

Specifications

Mechanical Detail