Signal Conditioner
Validyne Model CD15

Signal Conditioner Validyne Model CD15

Description
Features
Specifications
Instruction Manual
Typical CD15 Connections

Signal Conditioner Description:

The CD15 Signal Conditioner is a basic carrier demodulator which provides a +/-10 Vdc analog output over the full pressure scale of any Validyne variable reluctance pressure transducer.

The CD15 Signal Conditioner supplies a 5 Khz excitation to the transducer and provides zero balance and span adjustments mounted on ten-turn dials. The analog output signal is available from the front panel on two binding posts.

The CD15 Signal Conditioner also includes a low pass output filter which is flat to 1000 Hz.

The CD15 Signal Conditioner normally operates on 115 VAC power but models are available for 220 VAC and 12 Vdc. Output signal options include 4-20 mA, +/-1 Vdc and square root extraction.

Signal Conditioner Features:

• Provides +/-10 Vdc Output for any VR Transducer
• Compact for Bench Top
• 110 VAC Powered
• Easy to Use

Signal Conditioner Specifications:

Power:

95-125 VAC, 50-400 Hz (Std)
190-250 VAC, 50-400 Hz (Optional)
10.5 - 14.5 Vdc (Optional)

Output Signals:

+/-10 Vdc (Std)
+/-1 Vdc
4-20 mA
Square Root Outputs Available

Gain Range:

+/-15 to +/-75 mV/V Input
for +/-10 Vdc FS Output
Zero & Span Adjustments

Low Pass Filter:

1000 Hz

Size & Weight:

5.6" x 5.5" x 3"
3.5 Lbs

Typical Connections

CD15 Carrier Demodulator Instruction Manual

Description

The CD15 Signal Conditioner is a sine wave carrier demodulator designed to operate with variable reluctance transducers to provide a DC output signal for dynamic as well as steady state pressure measurements. The instrument furnishes regulated carrier excitation of 5 Vrms, 5 Khz sine wave to the two inductance arms of the pressure transducer. The sensor output is demodulated, amplified and filtered to produce a +/-10 Vdc analog output for the full scale range of the pressure transducer. The low impedance sine wave excitation allows the CD15 Signal Conditioner to be located several hundred feet away from the pressure transducer.

Zero and span controls are provided to adjust for unbalance in the system and to set the output gain of the demodulator to match the transducer sensitivity. An external balance pin is provided for additional permanent zero offset capability. All circuits are operated from a built-in regulated +/-15 Vdc power supply. Power is from 110 VAC , 60 Hz line (standard version).

Controls and Connections

Two ten-turn potentiometers with locking dials are located on the front panel . One control is for setting the zero adjust and the other for setting span during calibration.

Two terminal posts, one red (+) and one black (-) are located on the front panel for the DC signal output.

A toggle on/off power switch is located on the front panel for energizing the instrument and applying power to the transducer connected to the CD15. The unit also contains an LED pilot light which comes on when power is applied.

A 115 VAC, 60 Hz power cable (standard) plugs into any standard AC outlet. A transducer connector is mounted on the rear panel and connects to the cable from the variable reluctance pressure sensor. This connector may be a six-pin Bendix type, PT02A-10-6P or a 4-pin Cannon type, WK4-32S.

Options

A complete breakdown of options as defined by the model number is given.

Technical Characteristics

Installation

The CD15 Signal Conditioner can be operated on a bench or attached to a panel for rack-mounting. Transducers are connected to the CD15 by means of the connector on the rear panel. Cable shields should be connected to the shells of the mating connectors. In cases where the transducer body is grounded, the shield connection at the transducer end should be left open in order to eliminate noise from possible ground currents. See also Cabling Considerations.

The only electrical connections required are plugging the instrument into the appropriate power source, connection of the transducer cable and connection of the output binding posts to the receiving instrument.

Transducer Calibration

1. Connect the transducer cable to the connection on the back panel. Note: The same transducer cable should be used during calibration as in actual use as variations in cable lengths can affect the span settings.

2. Connect the transducer to a pressure source, and bleed the system .

3. Connect a voltmeter to the red (+) and black (-) output posts on the CD15 front panel. (See Diagram)

4. Reduce the input pressure to 0, and adjust the front panel zero control for an output of 0 Vdc.

5. Apply full scale pressure to the transducer and adjust the span control for +10 Vdc ouput. Note that any full scale output voltage may be set, from 0 to +10 V.

6. Reduce the pressure to 0 and re-chck the output, adjusting the zero control as necessary. Engage the zero and span adjustment locks.

7. The transducer, cable and CD15 Signal Conditioner are now calibrated together as a system. Record the zero and span dial settings. When multiple transducers are used with the same CD15, record zero and span settings separately as each transducer will have a unique pair of settings.

Transducer Connector Pin Connections

For Models With Six-pin Bendix PT Style Connector:

For Models With Four-pin Cannon WK4 Style Connector:

Outline Drawing

Cabling Considerations for Variable Reluctance Pressure Sensors

Variable Reluctance pressure sensors operate on an inductive sensing principle that requires and AC excitation and returns an AC signal. Long cabling runs from the sensor to the carrier demodulator are possible without compromise in performance if the proper cable configuration is observed. This application note describes recommended cable geometries for variable reluctance sensors such as models DP15, DP45 or DP103.

The purpose of using the correct cabling configuration is to minimize cross-talk between the carrier wires and the signal wires. If the distance between the sensor and carrier demodulator is just a few feet, no precautions are necessary: even loose pigtail leads will be sufficient. If the distance between the demodulator and sensor is over ten feet, it is best to select one of the cable geometries shown in the diagram below.

The optimal cable type consists of two pairs of separately shielded wires. This is the standard used for all Validyne cable assemblies. Belden #8434 cable has an inner-shielded pair (red and black) and an outer pair (green and white). The two inner-shielded wires are connected together to form the signal line, and this is wired to pin 2 or pin B of the cable connector. The green wire is the positive phase of the carrier, wired to pin A or pin 1, and the white wire is the negative carrier wired to pin 4 or pin D. The signal line is shielded from the excitation wires so that inductive cross-talk to the pressure signal is minimized.

The shields of the cable are generally connected to the connector shell, which, in turn, is mechanically connected to the demodulator and transducer housings. In cases where a difference in ground potential is expected between the plumbing and electronics, the shield should be disconnected at the transducer.

The following diagram shows various possible cabling configurations:

Typical Setup