A&A Supplement Ser., Vol. 126, November II 1997, 151-160
Received December 23, 1996; accepted February 24, 1997
S. Gaertner 
,
A. Benoıt 
,
J.-M. Lamarre 
,
M. Giard ,
J.-L. Bret ,
J.-P. Chabaud ,
F.-X. Désert ,
J.-P. Faure ,
G. Jegoudez ,
J. Landé ,
J. Leblanc ,
J.-P. Lepeltier,
J. Narbonne ,
M. Piat ,
R. Pons ,
G. Serra ,
and G. Simiand
Send offprint request: S. Gaertner, gaertner@cesr.cnes.fr
Centre d'Etude Spatiale des Rayonnement
s, 9 avenue du Colonel Roche,
BP. 4346, F-31028 Toulouse Cedex 04, France
Centre de Recherche des Très
Basses Températures, 25 avenue des Martyrs,
BP. 166, F-38042 Grenoble Cedex 09, France
Institut d'Astrophysique Spatiale,
Université Paris XI, Bât. 121,
F-91405 Orsay Cedex, France
A new readout electronic system for bolometers is presented in this paper.
The bolometer resistance is measured in a bridge with a capacitive load,
using a periodic square wave bias current. The bias voltages at both ends
of the bridge are balanced in order to keep the middle point around zero.
Only changes around this zero value are amplified and detected
synchronously with the bias signal. These features shift the measurement
frequency out of the electrical low frequency noises (JFETs), and reduces
the dynamics required from the amplification chain. The bias voltages are
fully controlled by computer, and the lock-in detection is digital. This
readout electronic has many advantages over previous ones. In particular,
it proved to be able to read the total power of the radiation reaching the
bolometer, and to perform measurements down to low frequencies (
Hz) without significant additional noise. These features open new
observation strategies such as full sky scanning to bolometer instruments
on board future submillimetre space projects having high thermal background
levels (warm telescope). The different steps of the development of this new
readout electronics on the ground-based Diabolo experiment are described,
the performances reached are discussed, and a version suitable for the
readout of the arrays of bolometers on the COBRAS/SAMBA satellite mission
is presented.
keywords: instrumentation: detectors; instrumentation: photometer -- methods: data analysis -- methods: numerical