CMN thermometer
The CMN (Cerium Magnesium Nitrate) thermometer can be used in a
temperature range between 4K and about 3mK. The paramagnetic salt
folows the Curie law, so the magnetisation is inversely proportional to the
temperature. The thermometer can be calibrated against a super
conducting fixed point device. The graph below shows an example of the
calibration of a CMN thermometer with a fixed point device. The
temperature is given by:
T = B / (M-A) [mK]
Digital Mutual Inductance Bridge
DMIBUSB
Milli-Kelvin Technologies
Kenauweg 11
2331 BA Leiden
The Netherlands
Tel: +31 6 58617419
Fax: +31 71 5722734
www.milli-K.com
info@milli-K.com
www.milli-K.com
Digital Mutual Induction Bridge
DMIB-USB
Digital Mutual Induction Bridge
Program
The Mutual Induction Bridge type MIB-USB is a fully automatic mutual induction
bridge for measurement of cryogenic temperatures. A small mutual inductor is used
as a four-wire temperature sensor, connected to the bridge electronics. As there is a
well- defined relation between Mutual Inductance and absolute temperature, the
output reading of the bridge may be calibrated straightforwardly in Kelvin.
The main window of the MIB
program. Three sensors can
be read simultaneously (in the
picture only sensor 1 and 2
are active). Each sensor can
be activated separately in the
parameter menu.
The hybrid bridge concept combines optimal noise reduction and high accuracy. As
frequency is continually adjustable between 5 Hz and 4 KHz, an optimum with the
lowest possible influence of interfering signals may always be found. The excitation
current can be adjusted between 100 pA and 10 mA. Three sensors may be
connected and measured simultaneously. The bridge is self-calibrating, the value of
the mutual inductance dependent only on one high precision 10 ohm resistor.
Signal generation and digitalization is performed with a National Instruments
multifunction I/O (NI USB-6211) interface card integrated with the bridge. The bridge
electronics consists of a a current source, a low noise preamplifier/bridge, 50/60 Hz
notch filter, a variable gain amplifier and high quality anti-aliazing filters. Operation of
the bridge, signal analysis and filtering is the responsibility of a computer program in
the form of a dynamic linking library.
Specifications:
Range: 10 nH .. 10 Henry
Excitation current: 100 pA .. 10 mA
Frequency: 5 Hz .. 4 kHz.
Notch filter: 50 / 60 Hz (with jumpers on the motherboard)
Noise: < 1 nV / root Hz
Resolution: < 5 μKelvin at 10 mK
Mains voltage: 85 .. 265 Vac
Mains frequency: 47 .. 63 Hz
The calibration can be set in
the program to read the
temperature directly. In both
the graphic display and the
digital read out one can
choose to read the inductance
or the temperature.