Wide range precision micro-ohmmeter
High basic accuracy of 0.1%
Wide measurement range of 1µ
W
to 20k
W
Current reversal switch for detecting thermal emf effects
Current diversion switch for easy zero setting
Four terminal measurement using Kelvin clip leads
Battery operation with built-in charger
Switchable 20mV clamp for ‘dry circuit’ testing
AIM & THURLBY THANDAR INSTRUMENTS
BS407
BS407 wide range precision micro-ohmmeter
A dedicated but versatile instrument
The BS407 is an instrument which is fully optimised for the task of
accurate measurement of low resistances with a best resolution of
W.
It has applications beyond the testing of components such as mea-
suring the resistance of motor or transformer windings, the proper-
ties of materials, the thickness of plates, the security of pipework
joints or wiring installations and many others.
It uses a Direct Current technique to measure true resistance,
rather than the resistive component of impedance which is shown
by AC excited RLC bridges. The test current for each range has
been carefully chosen to minimise heating of the sample under test
while being sufficient to minimise the effects of thermal emf and
noise.
This gives much greater accuracy at low resistances than can be
obtained from the very low test currents used by general purpose
high resolution multimeters. The low-noise low-drift bipolar amplifi-
ers employed need much less noise filtering than alternative chop-
per stabilised technologies resulting in faster settling to the correct
reading.
Battery operation with built-in charger
The BS407 is a fully portable instrument which operates from NiMh
rechargeable batteries. The battery charger is built into the instru-
ment and can be operated continuously during bench use.
Rapid 4-terminal measurement
The BS407 uses a four terminal measurement system via high
quality Kelvin Clip leads (supplied).
For speed and convenience front panel switches are provided for
current diversion (allowing in-situ zero adjustment) and current re-
versal (for identifying thermal emf errors).
An indicator lamp confirms correct flow of the measuring current
thus preventing spurious results from being recorded.
Wide measurement range
The BS407 has eight push-button selected decade measurement
ranges from 1.999mWup to 19.99kW.
This unusually wide range makes it suitable for a greater variety of
applications than other micro-ohmmeters.
A front panel operated ‘clamp’ switch is available to limit the maxi-
mum voltage across the unknown to 20mV. This is a requirement
for the measurement of switch contact resistances to international
standards.
High resolution and accuracy
With a lowest range of 1999µWthe BS407 can resolve down to one
micro-ohm. Rapid settling minimises delay between readings.
Precision analogue circuitry ensures a high measurement accu-
racy of up to 0.1% of reading ± 0.1% of scale.
RANGES AND ACCURACY
Accuracies apply for a one year period over a temperature range of 18oC to
28oC after a warm-up period of 5 minutes with the instrument and test con-
nections in thermal equilibrium. Tempco outside this range <±45ppm/oC
Range Resolution Test Current F.S. Voltage Accuracy
1999 µWW250 mA 500 µV ± 0.1% reading ± 0.4% scale
19.99 mW10 µW50 mA 1 mV ± 0.1% reading ± 0.2% scale
199.9 mW100 µW10 mA 2 mV ± 0.1% reading ± 0.1% scale
1999 mW1mW5 mA 10 mV ± 0.1% reading ± 0.1% scale
19.99 W10 mW500 µA 10 mV ± 0.1% reading ± 0.1% scale
199.9 W100 mW50 µA 10 mV ± 0.1% reading ± 0.1% scale
1999 W1W50 µA 100 mV ± 0.1% reading ± 0.1% scale
19.99 kW10 W10 µA 200 mV ± 0.1% reading ± 0.2% scale
FACILITIES
20mV Clamp
Operated by front panel switch. Limits the open circuit voltage across the un-
known to 20mV (+0mV, -4mV) for “dry circuit” testing of switch and relay con-
tacts. Not available on the 2000Wand 20kWranges.
Reverse Polarity
Operated by front panel switch. Reverses the polarity of the test current, en-
abling thermal emf effects to be detected and quantified.
Set Zero
Rotary offset control. A front panel switch can be used to divert the test cur-
rent way from the unknown, allowing zero adjustment to be undertaken with
the test leads in place.
MEASUREMENT SOURCE
Source EMF 18 mV ± 2mV with 20mV Clamp Active
< 6V with 20mV Clamp Inactive
Compliance > 1V (> 0.5V on 1999µWrange).
Compliance is the
maximum voltage that can be tolerated from additional
resistance in series with the force connections Thurlby Thandar Instruments Ltd. operates a policy of continuous development and reserves
the right to alter specifications without prior notice.
PROTECTION
The instrument is protected against the back-emf of its own test current from
any inductance and against external short-term connection to voltage sources
up to 50V.
Protection against greater abuse is provided by non-flammable fusible resis-
tors.
POWER SOURCE
Battery
Four internal Ni-MH cells (non removable). Operating time depends upon the
test current flowing - >150 hours with no test current, > 8 hours with maximum
test current (1999µWrange). Low battery indication in display.
AC Line
Built-in battery charger allows instrument operation while re-charging.
Nominal re-charge time 12 hours.
GENERAL
Display: 3.5 digit LCD with 12.5mm characters.
Casing: ABS casing with metal tilt stand giving approx. 15oangle.
Power: 220 - 240V, 110 - 120V or 100V ±10%, 50/60Hz, adjust-
able internally; 20VA max. Installation Category II.
Operating Range: +5oC to + 40oC, 20% to 80% RH.
Storage Range: -10oC to +50oC
Environmental: Indoor use at altitudes to 2000m, Pollution Degree 2.
Electrical Safety: Complies with EN61010-1.
EMC: Complies with EN61326.
Size: 220(W) x 88(H) x 230(D) mm, (10.3 x 3.4 x 9.2")
excluding feet and tilt stand.
Weight: 1.3 kg (3lb).
ACCESSORIES
SUPPLIED
Supplied with Kelvin Test Clip Leads, Operating Manual, IEC Mains Lead
OPTIONAL
Carrying Case
Designed and manufactured in Europe by:
Thurlby Thandar Instruments Ltd.
Glebe Road, Huntingdon. Cambs. PE29 7DR U.K.
Tel: +44 (0)1480 412451 Fax: +44 (0)1480 450409
Email: info@aimtti.com Web: www.aimtti.com
82100-1130 Iss. 1A
Thurlby Thandar Instruments Ltd.
Glebe Road, Huntingdon, Cambridgeshire PE29 7DR England (United Kingdom)
Tel: +44 (0)1480 412451 Fax: +44 (0)1480 450409
Email: info@aimtti.com Web: www.aimtti.com
Designed and built in Europe by:
Company name and product brands
Thurlby Thandar Instruments Ltd. (TTi) is one of Europe’s leading
manufacturers of test and measurement instruments.
Products have been sold under two brand names:
TTi and Aim.
In the future, however, the full product range will be branded Aim-TTi.
This changeover will be gradual and many products will continue to carry
the TTi or Aim brands for some time to come.
Web Addresses (URLs)
The preferred URL for obtaining information concerning Aim-TTi products
is:
www.aimtti.com (international customers)
Customers in the UK should use the URL:
www.aimtti.co.uk
Customers in the USA should use the URL:
www.aimtti.us
Note that previous URLs such as www.tti-test.com will continue to operate
for the time being.
Product Summary
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regulation technologies.
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pulse generators.
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current probes.
RF and EMC Test Equipment
Spectrum analyzers, signal generators, frequency counters,
power meters, emc measurement instruments.