, Volume 32, Issue 1, pp 17–22 | Cite as

Development of an Automated Precision Direct Current Source for Generation of pA Currents Based on Capacitance Charging Method at CSIR-NPL

Original Paper


The design and development of a direct current source for picoampere currents based on capacitance charging technique at CSIR-NPL is presented. A highly linear voltage ramp generator has been realized which can generate ramps with any rate between  ±1 and ±100 mVs−1. The ramp generator is computer controlled where the amplitude, slope and duration can all be controlled in software developed in LabVIEW which greatly simplifies the hardware configuration while providing great operational flexibility. The experimental evaluation of the current generator in the range from 1 to 100 pA indicates satisfactory performance. This work aims at developing a facility to ensure that CSIR-NPL can provide traceable calibration for picoammeters and electrometers.


Capacitance charging Current generator Ramp generator Calibration Electrometer 



The authors would like to extend their gratitude to Dr. V.N. Ojha, Head Apex Level Standards and Industrial Metrology (ALSIM), NPL for his constant support and encouragement. Thanks are also due to director NPL for providing all the facilities. Authors would also like to express their gratitude to the anonymous referees for their valuable comments to improve the manuscript.


  1. [1]
    G. D. Willenberg, H. N. Tauscher, and P. Warnecke, A Traceable Precision Current Source for Currents Between 100 aA and 10 pA, IEEE Trans. Instrum. Meas., 52 (2003) 436–439. DOI: 10.1109/TIM.2003.810051.CrossRefGoogle Scholar
  2. [2]
    H. E. van den Brom, P. de la Court,and G. Rietveld, Accurate Subpicoampere Current Source Based on a Differentiating Capacitor With Software-Controlled Nonlinearity Compensation, IEEE Trans. Instrum. Meas., 54 (2005) 554–558. DOI: 10.1109/TIM.2004.843127.CrossRefGoogle Scholar
  3. [3]
    L. Callegaro, V. D’Elia, and B. Trinchera, A Current Source for Picoammeter Calibration, IEEE Trans. Instrum. Meas., 56 (2007) 1198–1201. DOI: 10.1109/TIM.2007.900128.CrossRefGoogle Scholar
  4. [4]
    G. D. Willenberg and H. N. Tauscher, Novel Digital Voltage Ramp Generator for Use in Precision Current Sources in the Picoampere Range, IEEE Trans. Instrum. Meas., 58 (2009) 756–760. DOI: 10.1109/TIM.2008.2010675.CrossRefGoogle Scholar
  5. [5]
    L. Callegaro, P. P. Capra, V. D’Elia and F. Galliana, Generation of Reference DC Currents at 1 nA Level, with the Capacitance-Charging Method, IEEE Trans. Instrum. Meas., 63 (2014) 1779–1782. DOI: 10.1109/TIM.2014.2298694.CrossRefGoogle Scholar
  6. [6]
    H. Scherer, G. D. Willenberg, D. Drung, M. Götz, and E. Pesel, Traceable Precision Generation And Measurement of Pa Direct Currents (2014),
  7. [7]
    L. Callegaro,V. D’Elia,P. P. Capra and A. Sossco, Techniques for Traceable Measurements of Small Currents, IEEE Trans. Instrum. Meas., 56(2),April 2007. DOI: 10.1109/TIM.2007.890800.
  8. [8]
    S. P. Giblin, G. D. Willenberg, and N. E. Fletcher, Frequency Dependence Of Gas-Dielectric Capacitors Used In sub-nA Reference Current Generators, 2010 Conference on Precision Electromagnetic Measurements, Korea, 2010, pp. 318–319.Google Scholar
  9. [9]
    M. F Gard, Electrometers, in Wiley Survey of Instrumentation and measurement, (Edited by Stephen A. Dyer), John Wiley and Sons (2004) 293–301.Google Scholar
  10. [10]
    Keithley Instruments, Inc., Low level Measurements Handbook, Cleveland, 6th Edition, (2004) 2.15–2.73.Google Scholar
  11. [11]
    W. S. Kim, M. S. Kim, D. bee Kim, Y. G. Kim and P. G. Park, A Precision DC Low-Current Source for Calibration of Electrometers in the Range Of 100 pA To 1 fA,

Copyright information

© Metrology Society of India 2016

Authors and Affiliations

  • Bushra Ehtesham
    • 1
  • Poonam Sethi Bist
    • 1
  • Thomas John
    • 1
  1. 1.LF HF Impedance and DC Standards, ALSIMCSIR-National Physical LaboratoryNew DelhiIndia

Personalised recommendations