GRAS - AllianTech
¼″ Preamplifier Type 26TC, Built-in TEDS
Product Data
Typical Applications
■ General-purpose preamplifier
■ High-frequency measurements
■ High-pressure measurements
■ Multi-channel measurements
Special Properties
■ Wide Frequency Range
■ Low Noise Level
■ Very Small
■ Built-in TEDS1
Description
The G.R.A.S. ¼″ Preamplifier Type 26TC is a small
robust unit optimised for acoustic measurements
using condenser microphones. It has a very low
inherent noise level, a wide dynamic range and
a frequency response from below 2 Hz to above
200 kHz.
The Type 26TC is delivered with a built-in TEDS 1
chip and can be programmed as a single unit with
a microphone fitted.
Type 26TC, Vers. 12.05.2009
Design
All G.R.A.S. microphone preamplifiers are based
on a small ceramic thick-film substrate with a very
high input impedance. The ceramic substrate is
shielded by a guard ring to minimise the influence
of stray capacitance and microphonic interference.
The casing is made of stainless steel for maximum
strength and durability. The small dimensions of
this preamplifier ensure reliable operation under
humid conditions owing to the heat generated by
internal power dissipation.
Dynamic Range
Type 26TC can handle both single and dual-sided
power supplies. The supply can vary between
28 VDC and 120 VDC single-sided or ±14VDC and
±60 VDC dual-sided. When using the high supply
voltage (120VDCor ±60VDC), the dynamic range
exceeds 140 dB.
Noise
The electrical circuit in Type 26TC is built on a
ceramic substrate using selected low-noise com-
G. R . A . S.
SOUND & VIBRATION
Fig. 1 ¼″ Preamplifier Type 26TC, Built-in TEDS
ponents to gain very low self-noise. The electrical
self-noise is so low that system noise is mainly
determined by the microphone capsule’s thermal
noise.
Frequency response
The low-frequency cut-off of the Type 26TC preamplifier is mainly determined by the input impedance
of the preamplifier and the capacitance of the microphone capsule (see Fig. 3). The capacities 20 pF,
6.5 pF and 3 pF equal the typical capacitances of
½″, ¼″ and ⅛″ microphone capsules respectively.
The high-frequency cut-off is determined by the
preamplifier’s ability to drive capacitive loads (slew
rate), caused by the cable. For large-signals, the
effects of these parameters must be accounted for
when measurements are performed. Fig. 4 shows
the large-signal response for Type 26TC for various
capacitive loads corresponding to different cable
lengths. The output level is in decibels relative to
1 Volt. Typical capacitance for the cable is 100pF/m
(30pF/foot).
Connector
Preamplifier Type 26TC (Fig. 1) is provided with a
3-m lightweight cable terminating in a 7-pin LEMO
series 1B plug (Fig. 2). The cable is only 2.5 mm
in diameter and will withstand temperatures from
o
-40 oC to +150
adapter
for G.R.A.S.
LEMO C.
PlugAn
1B male
(external(GR0010)
view)
½″ microphones is included.
Power Supply + (6)
TEDS (5)
(1) Not used
(2) Signal Ground
Signal Output (4)
(3) Polarization 200 V
(7)
Power Supply –
(Ground)
Fig. 2 7-pin LEMO plug 1B male (ext. view)
1
Transducer Electronic Data Sheet - as specified by
IEEE-P1451.4
Skovlytoften 33,
2840 Holte, Denmark
www.gras.dk gras@gras.dk
¼″ Preamplifier Type 26TC, Built-in TEDS
Specifications
26AC
5
35
0
pF
dBVrms
20
pF
6.5
m
/1
3p
F
pF
dB
0
10
1n
0
pF
nF
10
1
10000
100000
1000000
Hz
Fig. 3 Typical low-frequency response of Type 26TC
for ½″ (20 pF), ¼″ (6.5 pF) and ⅛″ (3 pF) microphones
Technical Data
Fig. 4 Typical max. rms output signal with 120 V and
30 V supply
Accessories
Frequency response (18pF/small signal):
2 Hz - 200 kHz. . . . . . . . . . . . . . . . . . . . . . . .± 0.2 dB
Slew rate:
Input impedance:
0m
/1
1000
Hz
nF
0
100
1000.0
100pF
10n
10
100.0
nF
10.0
nF
m
00
/1
0
1.0
100n/1km
100n
5
10
0.1
10n/100m
30 V
10
-30
1
nF
15
km
3pF
/1
6.5pF
20
10
20pF
-20
-25
1n/10m
nF
-15
100pF/1m
25
0
10
-10
120 V
30
-5
20 V/µs
Included
GR0010:
¼″ to ½″ adapter for use with
G.R.A.S. ½″ microphones
Optional
20 GΩ, 0.4 pF
RA0001:
Output impedance (Cs = 20 pF, f = 1000Hz):
Typical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Ω
Right-angled (90º) Adapter for
½″ microphone and ¼″ preamplifier
Noise (measured with 20 pF ½″ dummy mic.):
A-weighted: . . . . . . . . . . . . . . . . . . . . . ≤ 2.5 µ V rms
(typically 1.8 µ V rms)
Linear (20 Hz - 20 kHz): . . . . . . . . . . . . . ≤ 6 µ V rms
(typically 3.5 µ V rms)
RA0003:
Adapter for ½″ microphone and
RA0006:
Angled (90º) Adapter ¼″ to ¼″.
Gain:
Typical: . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 0.25 dB
AA0008:
Extension cable, 3 metres
AA0009:
Extension cable, 10 metres
AA0012:
Extension cable, 30 metres
Maximum signal-output voltage (peak):
from ± 10 V to ± 50 V
AA0014:
Extension cable, 100 metres
Temperature:
Operation:. . . . . . . . . . . . . . . . . . . . -30 oC to + 70 oC
Storage: . . . . . . . . . . . . . . . . . . . . . - 40 oC to + 85 oC
AA0020_XX:
¼″ preamplifier
Power supply:
Single: . . . . . . . . . . 28 V (0.7 mA) to 120 V (2.5 mA)
Dual: . . . . . . . . . . . ± 14 V (0.7 mA) to ± 60 V (2.5 mA)
Extension cable, XX metres
(customer-specified length)
AA0013:
Relative humidity:
Operation:. . . . . . . . . . . . . . . . . . . . . . . . . 0 to 95 %
Storage: . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 95 %
RA0096:
Tripod adapter for ¼″ preamplifier
Tripod adapter for ¼″ preamplifier
with angular adjustment
Dimensions and Weight:
Diameter: . . . . . . . . . . . . . . . . . . . . . . 6.35 mm (¼″)
Length: . . . . . . . . . . . . . . . . . . . . . . . . .43 mm (1.7″)
Weight (without cable): . . . . . . . . . . . . . 6 g (0.2 oz)
Weight (with cable + LEMO conn.): 50 g (1.8 oz)
Type 90TP:
2
TEDS Editor Kit 2
For further information, refer to Product Data sheet
for ¼″ TEDS microphones.
G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.
G. R . A . S.
SOUND & VIBRATION
Skovlytoften 33,
2840 Holte, Denmark
www.gras.dk gras@gras.dk
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