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Models CTI - CT3

Automatic Comparators for Instrument Transformers

CTI: Current Transformers Comparator
CT3: Voltage Transformers Comparator

  • Ratio error and phase angle measurement on current and voltage instrument transformers
  • Measurements can be performed at the laboratory or in the field

Common characteristics of both models:

  • Based on inductive dividers with very long term stability
  • The measurement process is step by step guided by the software Windows(r) based 
  • All the measurements are done fully automatic
  • The software can compensate the error of the reference standard transformer used
  • The Test Report can be recorded and printed
  • Both Comparators CTI and CT3 can be operated without the PC and software, using an external oscilloscope
  • CTI and CT3 can be supplied in a single cabinet or as separate units

Characteristics of Model CTI:

  • Only a Standard Transformer with secondary nominal current of 5A is needed to calibrate transformers with 1 A or 5 A of secondary current
  • Tests can be performed according to IEC, VDE or IEEE-ANSI Standards
  • A digital ammeter is included

Characteristics of Model CT3:

  • Transformers with different voltage ratios can be easily compared 
  • A digital kilovoltmeter is included for primary voltage reading


These new models of current and voltage transformers comparators replace the old manually balanced bridges that CONIMED manufactured for more than 20 years. The hardware and software are designed to perform measurements in a very simple way, avoiding operator mistakes. The test reports can be obtained immediately after measuring, and easily recorded and printed.

The software goes step by step through the whole measurement process, stating the selected burden, current or voltage adjusting, and the ratio and phase errors are calculated. The WindowsTM based software makes everything easier.
If desired, the CTI and CT3 can be used with an oscilloscope instead of the PC and software.


Specifications - CTI

Current range: 50 mA - 10 A , (depending on the secondary nominal current and accuracy class of the sample transformer)
Error measurement range:
Accuracy Class 0.2 S (or 0.1) up to 1 - ( IEC )
Accuracy Class 0.3 to 1.2 - ( ANSI)

Error measurements do not depend of frequency
Accuracy and resolution of error measurements in automatic mode:
Resolution: 0,01 % - 0,01 cr ( 0,3 min)
Accuracy: 0,02 % - 0,03 cr ( 1 min)

Standard transformer, nominal secondary current: 5 A
Sample transformer, nominal secondary current: 1 A or 5 A
Measurement of test current up to 199,9 % with 0,1 % resolution

Specifications - CT3

Ratio of the sample transformer voltage ratio
to the standard transformer voltage ratio: 0,5 < k
x / kn < 4,4

Frequency range: 50 - 60 Hz
Accuracy and resolution of error measurements in automatic mode:
Resolution: 0,01 % - 0,01 cr ( 0,3 min)
Accuracy: 0,02 % - 0,03 cr ( 1 min)
Measurement of test voltage: up to 300 V of secondary voltage (transformer under test)


  • Standard Current and Voltage Transformers
  • Burdens


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