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A&A Supplement Ser., Vol. 126, November II 1997, 151-160

Received December 23, 1996; accepted February 24, 1997

A new readout system for bolometers with improved low frequency stability

S. Gaertner tex2html_wrap1063, A. Benoıt tex2html_wrap1065, J.-M. Lamarre tex2html_wrap1067, M. Giard tex2html_wrap1063, J.-L. Bret tex2html_wrap1065, J.-P. Chabaud tex2html_wrap1063, F.-X. Désert tex2html_wrap1067, J.-P. Faure tex2html_wrap1065, G. Jegoudez tex2html_wrap1067, J. Landé tex2html_wrap1063, J. Leblanc tex2html_wrap1067, J.-P. Lepeltiertex2html_wrap1067, J. Narbonne tex2html_wrap1063, M. Piat tex2html_wrap1067, R. Pons tex2html_wrap1063, G. Serra tex2html_wrap1063, and G. Simiand tex2html_wrap1065

Send offprint request: S. Gaertner,
tex2html_wrap520 Centre d'Etude Spatiale des Rayonnement s, 9 avenue du Colonel Roche, BP. 4346, F-31028 Toulouse Cedex 04, France
tex2html_wrap520  Centre de Recherche des Très Basses Températures, 25 avenue des Martyrs, BP. 166, F-38042 Grenoble Cedex 09, France
tex2html_wrap520 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 (tex2html_wrap_inline1051 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

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