Audio Precision APx1701 Series, Installation Instructions Manual, Page: 40 / 44

Chapter : User’s Guide
22 APx1701 Transducer Test Interface: User’s Guide
Microphone Powering and the
APx1701
Condenser microphones (also called
capacitor micro-
phones
) use a capacitor as the transducer element. All con-
denser microphones require powering of some sort. Some
designs need a polarizing voltage for the transducer ele-
ment, and all designs need power for the small amplifier
and associated circuitry attached to the transducer.
Measurement microphone CCP powering
Measurement microphones that are pre-polarized (using an
electret
condenser for the transducer element) are typically
powered by a constant current supply (CCP) power system.
The APx1701 can p24 Vdc CCP power at 4 mA to
such microphones when connected to the unbalanced
microphone inputs.
Measurement microphones that require a polarization volt-
age for the transducer element are typically fitted with a
multi-pin connector and are provided with a proprietary
power supply from the manufacturer. The APx1701 can use
such microphones, but cannot power them. You must pro-
vide a power supply.
Studio microphone phantom powering
Condenser microphones designed for recording and sound
reinforcement applications are typically balanced devices,
and use a powering system called phantom power.
A phantom powered microphone may be pre-polarized, or
may develop the polarization voltage internally from the
phantom power. The APx1701 can p48 Vdc phan-
tom power to such microphones when connected to the bal-
anced microphone inputs.
TEDS data
Some measurement microphones and other transducers
store Transducer Electronic Data Sheet (TEDS) informa-
tion that can be read by connected devices. The Audio Pre-
cision APx1701 Transducer Test Interface can read data
from TEDS 0.9 and TEDS 1.0 microphones connected to
either of the unbalanced microphone inputs. This data is
passed to the APx500 software via the USB connection for
display, reporting, and entry into calibration dialogs.
For R&D testing, these data are used as data-sheet values in
calibration reports. For production testing in controlled pro-
duction setups and environments, the TEDS data can be
used in lieu of actual calibration values.
For best accuracy, it is recommended that micro-
phone sensitivity be measured using an external
acoustic source such as a pistonphone.
TEDS is described in detail in the IEEE 1451 family of
standards.
APx1701 Self-Test
Audio Precision offers a diagnostic software program called
SelfTest.exe, which interrogates the attached hardware and
guides the user through a series of procedures to verify the
performance of many of the analyzer functions and circuits.
Go to the Audio Precision Web site and download the
APx500 Series Self-Test from the Software: Utilities, Proj-
ects & Macros section at ap.com.