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Thermometry Bridges

F18 Primary Thermometry Bridge

Features
		Accuracy: <0.1ppm (±25 micro K)
		Resolution: 0.003ppm (0.75 micro K)
		Linearity: <±0.01ppm)
		Stability: <0.02ppm/year
		Fast measurement time (2 second balance)
		Differential and absolute measurement
		Warm up time: <30 seconds

Typical Applications
		Primary Thermometer Calibration
		Research
		Oceanography
		Aerospace
		Power
		Thermometer manufacturers

F18 Brochure (PDF, approx 210KB)

For more information about this product contact ASL

A true pedigree

National standards laboratories around the world require the best instrumentation for their work. The majority of these organisations use ASL's top of the range Models F900 or F18 to set the temperature standard in their country, these include 23 out of the 24 members and observers of the international C.C.T. (Consultative Committee of Thermometry).

Traceable to International Standards

In world class metrology, the most important consideration is the quality of the fundamental measurement. ASL's F18 AC bridge technology represents the peak of performance in resistance thermometer measurement and exploits the inherent advantages of AC bridge technology to maintain repeatable measurements of the highest precision under practical operating conditions.

The Model F18 is designed specifically for resistance thermometry to provide you with the best possible accuracy. The 25Hz or 75Hz operating frequency provides fast, continuous measurement with high immunity to thermal emfs and supply frequency noise sources. Practical measurements involve cables, connectors and imperfect operating environments, the F18 achieves its full specification under a wide range of real operating conditions.

For example, you can add cable probe extensions and extra terminals junctions without concern for thermal emfs generated by the temperature gradients in your laboratory. Design features such as the unique input guard ensure that you really can obtain the specified accuracy of 0.1 ppm over the range of 0.2 ohms to 390 ohms. This equates to a temperature measurement accuracy of 25 micro K for a 25.5 ohm SPRT referenced to a 25 ohm reference resistor.

AC bridge technology will always out perform measurements made using DC technology with slow current reversal. To find out more, take a look at our AC vs DC information page.

The F18 includes a wide range of features specifically tailored for temperature metrology. These include programmable excitation current, root 2 current, analogue outputs, selectable source impedance, gain and filter bandwidth. Manual or automatic bridge balancing together with manual or automatic control (IEEE interface) of the instrument ensure that the Fl 8 can provide solutions in a wide range of measurement applications.

The F18 can be used with one or more switchboxes for multi-channel calibration.

F18 Primary Thermometry Bridge Features

See the table below for a run-down of this product's features and capabilities.

Bandwidth	Selectable: 0.5, 0.1 or 0.02 Hz
External Standard	AC/DC standard resistor or resistance thermometer
Sensor current	0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50mA or x root 2 any value
Sensor current frequency	User selectable frequencies:	25 or 75 Hz with 50 Hz supply 30 or 90 Hz with 60 Hz supply Phase locked to supply frequency
Bridge balancing modes	Automatic:	via full self balance algorithm
	Manual:	via front panel switches (to 0.1 ppm) and analogue meter (interpolated to 0.01 ppm)
Self check modes	Zero:	verifies bridge zero accuracy
	Unity:	verifies bridge slope accuracy
Lead connections	True four wire connections for resistance thermometer (Rt) and standard resistor (Rs). Accuracy is unaffected by series lead resistance, permitting measurements with long cables (100 metres for 25.5 Ohm SPRT referenced to a 25 Ohm resistor)
Quadrature balance	Eliminates effects of thermometer, resistor and cable reactance
Active input guard	Eliminates effects of leakage from any terminal to ground
Analogue output	Null balance:	±10V (unfiltered)
	Programmable:	0-10V (3 scale ranges)

For more information about this product contact ASL

Accessories

The following accessories are available for use with the F18.

SB148	10 channel auto/manual mulitplexer, with individual preset "keep warm" current
SB148/01	As SB148, with 4 individual "keep warm" currents per channel
SB158	Driver/interface for up to 2 x SB148 or 5B1 48/01 multiplexers (Specify RS232 or IEEE
SB158/01	Driver/interface for up to 6 x 5B148 or SB148/01 multiplexers (Specify R5232 or IEEE)
F18 AS1 System	F18 complete with SB148 and SB158 multiplexer in 19"/1 6U cabinet complete with power distribution and cutout
F18 AS2 System	As AS1 system, but with SB148/01 multiplexer
RW1, 10, 25, 100, 300	"Wilkins" AC/DC Standard Resistor. Values: 1, 10, 25,100 and 300 ohms
RWTE1	Thermal enclosure for 1 off RW resistor
FA1	Co-axial cable set with BNC connectors at both ends to use with FA-3 adaptor
FA2	Co-axial cable set with BNC connectors at one end for reference resistor
FA3	4 terminal to 2 x BNC connector, adapter box
FA-KIT	FA1, FA2 and FA3 cable set

For more information about the above accessories contact ASL

275 King Henry's Drive
New Addington
Croydon
CR0 0AE