Penny & Giles Controls Limited

 Nine Mile point Industrial Estate, Cwmfelinfach, Gwent, United Kingdom NP1 7JB.  Tel: (01495) 202000  Fax: (01495) 202006

PERFORMANCE AND APPLICATION DETAILS FOR

THE 8000 SERIES RANGE OF STUDIO FADERS

SCOPE

This document defines the performance and testing procedures of the 8000 Series range of studio faders.

NOTE: Where there is a conflict between this document and a Data Sheet, the Data Sheet shall take precedence.

RELATED DOCUMENTS

  i)        8000 series Catalogue P 63514

 ii)        Maintenance document RM 62227

iii)        BS 9130 - Specification for potentiometers of assessed quality: Generic data and methods of test.

 iv)       MIL-R-39023A - General specification for non-wire-wound, variable, precision resistors.

SAFETY WARNING

The 8000 Series range of faders is designed to operate at low voltages not exceeding 50 volts d.c..  Any connection to voltages above this level could cause serious injury or death to users.

CONTENTS

1.  Description of the 8000 Series range

2.  Definitions and terms used

3.  General performance specification

4. 

5.  Packaging

6. 

7.  Acceptance test methods

8.  Application Notes

RECORD OF ISSUES
ISSUE	CHANGE NOTE No.	PREPARED	ENGINEERING APPROVAL	QUALITY APPROVAL	DATE
3	ECR6350	L.BRAIN			14.5.99

1. Description of the 8000 Series Range

The 8000 Series range of professional studio faders are linear motion manual & motorised faders intended for use in audio, video and lighting control equipment. A wide range of options is provided to cater for most requirements, e.g. various resistances, output laws, track switches, microswitches, motors and motor positions.

2. Definitions and Terms Used

2.1 Faders With Audio Tapers - "LOG"

Law Accuracy                        The allowable deviation of output from the nominal value at a given point along the fader.

Cut-off (dB)                            Maximum attenuation of a fader expressed in dB, i.e. when the channel is closed (the ¥ dB position), relative to the input signal level.

Insertion Loss (dB)                The difference between the input signal and the output signal when the channel is fully open. (i.e. at the 0 dB position), expressed in dB.

Crosstalk (dB)                       The signal produced at the output of one track when a signal is applied to the other (stereo faders), expressed in dB, relative to input signal.  See Fig 1.

2.2 Faders With Linear Tapers - "LIN"

Absolute Linearity                 The maximum deviation of the fader output from a straight reference line drawn through the specified minimum and maximum output ratios. This is expressed as a percentage of the total applied voltage. Unless otherwise specified, minimum and maximum output ratios are 0 and 100% of the total applied voltage respectively. Refer to figure 2.

Additional information may be obtained from the relevant Standards (see 'related documents').

End Voltage                           The voltage between the wiper terminal and an end terminal when the knob bracket is positioned at the corresponding end point.  End voltage is expressed as a percentage of the total applied voltage.

Output Ratio                           The ratio of the output voltage to the total applied voltage.

2.3 VCA faders

End Voltage                           The voltage between the wiper terminal and an end terminal when the knob bracket is positioned at the corresponding end point. End voltage is expressed as a percentage of the total applied voltage.

Output Ratio                           The ratio of the output voltage to the total applied voltage.

2.4 All Faders

Total Applied Voltage           The total voltage applied between the designated input terminals.

Total Mechanical Travel       The total travel of the knob bracket between integral stops.

Matching Accuracy               Also known as Tracking Error, it is the allowable deviation of output from channel 1. (Stereo faders only).

Insulation Resistance            The minimum resistance between track to earth and track to track.

                                                 500V is used for this measurement to ensure no breakdown of

                                                 any components parts.

Wiper Load                            The external resistance as seen by the output voltage. Penny and Giles use 100KW for calibration and test purposes.

Loading Error                        The difference between the fader output with an infinite load resistance and with a specified finite load resistance, at any position, provided it is the same position for both output measurements.

2.5 Switches

Pre-fade Listen                     A track switch which operates at the 4/0V end of the fader, under spring load and before the track is opened. 

Fader Start/Auxiliary             A track switch or microswitch which operates within 4mm of the

                                                ¥ /0V end of the fader.

2.6 Servo Tracks

The servo track is nominally 2mm longer than the mechanical stroke.

The nominal end voltages are 990mV and 10mV (1v reference) and only in the extremes of tolerance are the end voltages achieved, thus allowing servo control over the full mechanical stroke.

3. General Performance Specification

Operating Temperature                                                        0°C to +50°C

Storage Temperature                                                           -20°C to +70°C

Maximum applied voltage                                                    50v d.c.

Maximum Wiper Current (including track switch)  2mA

Maximum Microswitch Current                                            100mA @ 30v d.c. (resistive load)

5. Packaging

Immediate                  Each fader is placed in a plastic bag

Primary                       Polystyrene container, 10 faders per package - where applicable.

Final                            Skillet containing a maximum of 10 primary packages - where applicable.

7.0 Acceptance Test Methods

It is important that the fader body is grounded via the mounting screws.

7.1 Insertion Loss and Audio Law

7.1.1 The following test equipment is required:-

Oscillator set at 1KHz (approx 5V output)

A.C. Microvoltmeter set to dB scale

100KW Wiper load

Single pole changeover switch

7.1.2 Connect the channel to the test equipment as shown in Figure 3.  With the switch in position 1, adjust the output of the oscillator such that the microvoltmeter reads 0dB.

7.1.3 Put the switch in position 2 and position the slider at 0dB. The reading on the meter is the insertion loss of the channel.

7.1.4 Law measurements can now be made by moving the slider to each position as specified in the fader's corresponding Data Sheet. (e.g. at -5dB, -10dB etc.), and reading the value on the microvoltmeter.

7.2 Infinity Cut-off

7.2.1 Repeat sections 7.1.2 and 7.1.3 but with the oscillator set to 15KHz.  The reading  on the Microvoltmeter when the slider is at the ¥ end stop is the cut-off value (dB).

7.2.2 It is essential that all leads are effectively screened when making cut off measurements.  Screens and fader body must be connected to a common earth point.

7.3 Audio Matching Accuracy (stereo faders)

7.3.1 The following test equipment is required:-

Oscillator set at 1KHz ( approx 5v output)

A.C. Microvoltmeter set to dB scale

100KW Wiper load

2 x Single pole changeover switches

7.3.2 Connect the tracks to the test equipment as shown in Figure 4.  Switch 'A' is used when measuring insertion loss and switch 'B' is used to switch from track 1 to track 2 when measuring matching accuracy.  With switch 'A' in position 1 and switch 'B' in position 1, adjust the oscillator output such that the microvoltmeter reads 0dB.

7.3.3 Adjust switch 'A' to position 2 and position the slider at 0dB.  The reading on the meter is the insertion loss of track 1.

7.3.4 Adjust switch 'B' to position 2, the reading on the meter is the output of track 2.  Compare this reading to track 1 to obtain the matching accuracy at 0dB.

7.3.5 Continue to measure the matching accuracy by using switch 'B' to select track1/track2 at each slider position, as specified in the corresponding Data Sheet. (e.g. at -5dB, -10dB etc.)

7.4 End Volts

7.4.1 The following test equipment is required:-

1 V D.C. Power supply

A.C. Microvoltmeter set to measure voltage

7.4.2 Measure the power supply to ensure stability and to determine its exact output value (within the limits of the microvoltmeter).  Connect the fader to the test equipment as shown in Figure 5.

7.4.3 Move the slider to each end of stroke and measure the output voltage.  At the 0%V end of the fader this reading is the end volts.  At the 100%V end of the fader, subtract the measured figure from the input voltage to obtain the end volts.

8.0 Application Notes

8.1       The body of the fader must be grounded effectively through the front panel of the desk, by tightening the two fader mounting screws to a torque of 50 cNm.  The front panel must be grounded effectively to the overall earth of the system.

8.2       It is recommended that the guard rail on stereo faders is effectively grounded for minimum crosstalk.

8.3       Typical Trackswitch circuit examples

Normally Open (Switch point typically 1 mm from ¥ end)

Normally Closed (Switch point typically 3 mm from ¥ end)

8.4 Typical Microswitch circuit example

Notes:-

*           If using microswitch in an inductive circuit, adequate protection must be provided to the        contacts as shown above.

*           When soldering to the terminals of the microswitch, ensure that the iron is not applied           for more than 5 seconds and that the tip temperature is maintained below 320°C.  Avoid        applying any force to the terminals.

*           The switch is not a completely sealed construction so do not attempt to clean.

*           Avoid using the fader in a corrosive or dusty atmosphere.

8.5       VCA circuit example