TTI BS407 Technical data

THURLBY THANDAR INSTRUMENTS

BS407 Wide range precision micro-ohmmeter

BS407 PRECISION MILLI/MICRO OHMMETER

i

T

T

ZERO ADJUST

mΩΩ

Polarity

µΩ

19.99 199.91999

250mA 50mA 10mA

1999 1999 19.9919.99 199.9

5mA

Force Current

20mV

Set

Operate

Clamp

Zero

Off
On

● High basic accuracy of 0.1%

●

Wide measurement range of 1 micro Ω to 20k Ω

●

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

Charge

Force on

µ µ

µ

500 A 50 A 50 A 10 A

to 20 kΩ1

µΩµΩµΩ

UNKNOWN

SENSE

kΩ

50Ω

+

µ

FORCE

_

A dedicated but versatile instrument

The BS407 is an instrument which is fully optimised for the task of accu
rate measurement of low resistances with a best resolution of 1µΩ.

Most multimeters offer a best resolution which is at least one thousand
poorer than this. A very high resolution multimeter may attempt to re­solvefairlylowresistances, butit doesso byresolving extremelylow volt­ages(typically one nano-voltper micro-ohm), makingit subjecttosevere
errors from thermal emf effects and noise.

In contrast, the BS407 generates sufficient test voltage across the un­known resistance to combat noise and reduce thermal emf effects to
manageable levels. Current reversal canthen beused to eliminate any
remaining thermal offset.

Rapid 4-terminal measurement

The BS407 uses a fourterminal measurent system via high qualityKel
vin Clip leads (supplied).

Forspeed andconveniencefront panelswitches areprovided for current
diversion (allowing in-situ zero adjustment) and current reversal (for
identifying thermal emf errors). An LED indicator warns of open circuit
leads thus preventing spurious results from being recorded.

Battery operation with built-in charger

The BS407 is a fully portable instrument which operates from NiMh re
chargeablebatteries.Thebattery charger is built into the instrumentand
can be operated continuously during bench use.

Wide measurement range

The BS407 has eight push-button selected decade measurement
ranges from 1.999mΩ up to 19.99kΩ.

Thisunusuallywide range makes it suitablefora greater variety of appli
cations than other micro-ohmmeters.

A front panel operated ‘clamp’ switch is available to limit the maximum
voltageacross the unknownto 20mV. This is arequirement for themea
surement of switch contact resistances to international standards.

High resolution and accuracy

Witha lowestrangeof1999µΩthe BS407canresolveonemicro-ohm.
Precision analogue circuitry ensures a high measurement accuracy of

up to 0.1% of reading ± 1 digit.

Designed and built in the EEC by:

Glebe Road, Huntingdon. Cambs. PE29 7DR United Kingdom

Tel: [phone] Fax: [phone]

e-mail: [e-mail] Web: http://www.tti-test.com

Thurlby Thandar Instruments Ltd.

RANGES AND ACCURACY

Accuracies apply over a temperature range of18oCto28oC after a
warm-up period of 30 minutes, and withthe test connections in thermal
equalibrium. Specificied accuracy applies for a period of one year.

Range Resolu

tion

1999 µΩ 1 µΩ

19.99 mΩ 10 µΩ

199.9 mΩ 100 µΩ
1999 mΩ 1 mΩ

19.99 Ω 10 mΩ

199.9 Ω 100 mΩ
1999 Ω 1 Ω

19.99 kΩ 10 Ω

Test Cur

­rent

250 mA 500 µV ± 0.1% r ± 0.4% scale

50 mA 1 mV ± 0.1% r ± 0.2% scale
10 mA 2 mV ± 0.1% r ± 0.1% scale

5 mA 10 mV ± 0.1% r ± 0.1% scale

500 µA 10 mV ± 0.1% r ± 0.1% scale

50 µA 10 mV ± 0.1% r ± 0.1% scale
50 µA 100 mV ± 0.1% r ± 0.1% scale
10 µA 200 mV ± 0.1% r ± 0.2% scale

F.S. Volt

­age

-

FACILITIES

20mV Clamp

Operated by front panel switch. Limits the open circuit voltage across
the unknown to 20mV (+0mV, -4mV) for“dry circuit” testing of switch
and relay contacts. Not available on the 2000Ω and 20kΩranges.

Reverse Polarity

Operated by front panel switch. Reverses the polarity of the test cur
rent, enabling thermal emf effects to bedetected and quantified.

Set Zero

­Operated by non-latching front panel switch androtary offset control.
Diverts the test current way from theunknown allowing zero adjust­ment to be undertaken with the testleads in place.

MEASUREMENT SOURCE

Source EMF 18 mV ± 2mV with20mV Clamp Active
Compliance

Complianceis the maximumvoltage thatcan betoleratedfromadditional
resistance in series with the force connections

< 6V with 20mV Clamp Inactive
> 1V (> 0.5V on 1999µΩ range).

PROTECTION

The instrument is protected against the back-emfof its own test current
from any inductance.

­The instrument is protected against external voltagesources delivering

up to one amp. Protection against greater abuse is provided by
non-flamable fusible resistors.

POWER SOURCE

Battery

Four internal Ni-MH cells (non removable). Operating time depends
upon the test current flowing - >150hours with no test current, > 8

­hours with maximum test current (1999µΩ range). Low battery indica

tion in display.

AC Line

Built-in battery charger allows instrument operation whilere-charging.
Nominal re-charge time 16 hours.

GENERAL

­Display: 3.5 digit LCD with 12.5mm characters.

Casing: ABS casing with metal tilt stand giving 15
Power: 230V or 115V ±14% 50/60Hz, adjustable internally;

­Operating Range: +5

Storage Range: -10

20VA max. Installation Category II.

o

Cto+40oC, 20% to 80% RH.

o

Cto+65oC
Environmental: Indoor use at altitudes to2000m, Pollution Degree 2.
Electrical Safety: Complies with EN61010-1.
EMC: Complies with EN61326.
Size: 220(W) x 82(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

Kelvin Test Clip Leads, Operating Manual, IECMains Lead

OPTIONAL

Carrying Case

Thurlby Thandar Instruments Ltd. operates a policy of continuous development
and reserves the right to alter specifications without prior notice.

Accuracy

o

angle.

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