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XL7900

Evacuated vibrating-membrane capacitor used as a DC-to-AC converter in electrometers, dosimeters, pH meters, and other very-high-input-resistance instruments. Its membrane resonates around 5.3–6.3 kHz, enabling modulation of extremely small DC measurement signals.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
Magnoval, gold plated pins
Socket code
B9E
Base pins
-
Nominal heater
-

Description

Vibrating membrane capacitor in an evacuated envelope, intended as a D.C.-to-A.C. converter for electrometers, dosimeters, pH meters, and other very-high-input-resistance instruments.

Socket description

Novar 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
Magnoval, gold plated pins
Socket code
B9E
Base pins
-
Nominal heater voltage
-
Nominal heater current
-
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

Magnoval, gold plated pins - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Other

X-ray radiationInterelectrode capacitances

No fixed ratings are recorded for this section.

Published electrical data additionally captured in parameter rows.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1999 Philips E-Z

Published operating points and test conditions from this source.

SECTION 1

Other

Characteristic

  • Equipment measuring currents of

    500

    Equipment measuring currents of 500 electrons per second have

  • Contact potential

    50 mV

    Contact potential -50to +50 mV

  • Short term drift of contact potential <

    100 uv

    Short term drift of contact potential < 100 uv

  • Insulation >

    1015

    Insulation > 1015 @

  • C,, = measuring capacitor

    9.1

    C,, = measuring capacitor 9.1¢

  • Contact potential over Cy =50 to

    50 mV

    Contact potential over Cy =50 to +50 mV

  • 1y Above

    40

    1y Above 40 ¢, it is possible that two capacitor plates will touch each other and

  • capacitors have a conversion efficiency between

    40

    capacitors have a conversion efficiency between 10% and 40%. Ly

  • capacitor terminals >

    2

    capacitor terminals > 1015 @ 2)

  • Resonance frequency of the membrane

    6.3 kHz

    Resonance frequency of the membrane 5.3t06.3 kHz

  • Capacitances of C, and Cqr

    35 pF

    Capacitances of C, and Cqr 35 pF

  • turned out that all capacitors have a conversion efficiency between

    40

    turned out that all capacitors have a conversion efficiency between 10 and 40%

  • at a voltage over L] of

    1

    at a voltage over L] of 1 VRMS.

Other

  • D.C. voltage on Cm max

    25 V

    D.C. voltage on Cm max. 25 V