5896 Transformer Micro Ohmmeter.
This high current, digital, direct reading, microprocessor based transformer Micro ohmmeter will measure the D.C. resistance of power transformers and other electrical devices where high inductance is also present. 

With a choice of single or dual measuring
channels (models 5896 or 5896B), this fast initial 
reading Micro ohmmeter provides the best overall 
solution for low resistance testing of transformers.

Small pole mounted transformers to large
distribution types with 3 or 5 limb construction
are easily measured using the 5896 as are
notoriously difficult transformer types
including 3 phase closed delta and auto-tap
changers. 

The 5896/5896B Transformer Micro-Ohmmeter provides  6 ranges from 2 milli-Ohms to 190 Ohms, 
a choice of 2 currents per range, up to 25A on the lower 2 ranges with 0.1% accuracy . 

The single or two channel measurement of primary or primary and secondary transformer windings are displayed on a large LCD screen to 4 1/2 digit resolution e.g. 19000.

An advanced, high power, wide ranging Ohmmeter for fast, accurate and sensitive measurements of transformers or other inductive loads. With built-in data storage and interfacing to PC or external printer. Suitable for a wide range of factory or on-site plant measurement and performance testing.

Micro Ohmmeter applications include: 

• Transformer dc winding resistance 
• Generator stator/rotor resistance
• Large Motors
• Power utility sub-stations
• Transformer tap-changer operation and contact tests 
• Routine plant maintenance and “Benchmarking” for fault finding 
• Factory testing to International Standards.
• Transformer “Heat-run” tests
• Power connections and circuit breaker testing.

Features 

• One or two independent measuring channels (5896B)
• High current (25A) 
• High accuracy (0.1%) 
• High resolution to 0.1µOhm 
• 4 1/2 digit large display to 19000 
• Wide measurement range 1 milli-Ohm to 190 Ohms 
• Rapid saturation to read time on Star-Delta transformers (>30 secs) 
• Hazard warning light and buzzer for high voltages
• Storage of data on internal memory 
• Built-in printer for time and readings records. 
• Constant current regulated supply eliminates L ^di/_dt effects 
• 6 ranges, choice of two currents/range 
• Large LCD screen for data presentation 
• RS232/IEEE488 computer interface 
• Over temperature protection

Model 5896, 5896B Micro Ohmmeter Technical data

The 5896/5896B fully automatic direct reading I or 2 channel precision transformer and high inductive load Micro Ohmmeter provides an unparalleled, high performance instrument. 
It combines high speed, wide range, 0.1% precision, 1 part in 19,000 resolution and 25A measuring current for sensitive low noise measurements. 

The micro ohmmeter is based on an internal micro-processor with menu driven options via front panel membrane keypad controls. The system operating procedure includes storage of any constants or variables and a calibration mode. This enables instrument calibration against known external standards to be made/stored via front panel keys. 

The 70 x 127 mm LCD display shows selected current, time, date, range and resistance values.

User controlled internal software allows data logging and storage of measurements in the instruments internal memory. The RS2323/IEEE488 interface enables stored data to be down loaded to a computer or external printer. The instrument may also be fully controlled via the interface.

The use of special current control circuits enables large transformers, particularly closed delta types, to be quickly saturated. This enables the initial first reading to be made within 60 seconds for most transformers. This is important when making “heat-run” tests to comply with various international standards. In addition the special circuits employed limit the Ldi/dt effects that can give rise to noise and unstable readings. 
When testing tap-changers, where accurate measurement of contact resistance of the taps is important, the high resolution of the 5896, to 1 part in 19,000, provides an accurate means to detect potential problems.