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Calibrating The Output Impedance of NI Signal Generators

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Overview

While it is not part of the official calibration procedure, NI provides users the ability to calibrate the output impedance of their Signal Generators.

Downloads

Filename: fgen_cal.zip
Requirements: View

Required Equipment: 

- Multi meter (DMM) with at least the following specifications:
           - DC Accuracy ≤ ±50 ppm
           - Resolution   ≤ 1 mV
- 50 ohms or 75 ohms feed-through.

Two measurements are required for each configuration to calibrate. One with the feed-through in place, and one without the feed-through. It is the ratio of these measurements that the driver will use to calculate the output impedance of the path. For increased accuracy, the NIFGEN driver provides the user options to calibrate each path, the post amplifier attenuator or the output impedance configuration, separately.

To perform these measurement follow the following steps:

  1. Measure the impedance of the feed-through that is to be used with the DMM.
  2. Generate a DC voltage by setting the path and the amplitude level corresponding to the desired post amplifier attenuation to calibrate. A quick reference table can be found below. It is important to note that these are not the only values that can be used but are provided only as a guide.
    The 5402/5406 do not allow a DC voltage to be generated on the low gain path, therefore they need to be configured for a square wave and then use a data mask to achieve a DC voltage on the low gain path. The fgen_output_generation_for_cal.vi found in the attached zipped folder fgen_cal.zip demonstrates how to do that.
  3. Measure the output level with the feed-through in place and document the voltage level. Then, remove the feed-through and take another measurement.
  4. Once all measurements have been taken use the impedance_calibration.vi to set the calibration constants on the device.

 

  

Requirements


Filename: fgen_cal.zip

Software Requirements


Application Software: LabVIEW Base Development System
Language(s): LabVIEW

Hardware Requirements


Hardware Group: Signal Source (AWG/FG/AO)
Hardware Model: PC-1500PFB, PXI-5441, PCI-5402, PCI-5406, PCI-5411, PCI-5412, PCI-5421, PCI-5422, PCI-5431, PXI-5102, PXI-5104, PXI-5112, PXI-5122, PXI-5401, PXI-5402, PXI-5404, PXI-5406, PXI-5411, PXI-5412, PXI-5421, PXI-5422, PCI-5401
Driver: NI-FGEN 2.6.1

 
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This example program (this "program") was developed by a National Instruments ("NI") Applications Engineer. Although technical support of this program may be made available by National Instruments, this program may not be completely tested and verified, and NI does not guarantee its quality in any way or that NI will continue to support this program with each new revision of related products and drivers. THIS EXAMPLE PROGRAM IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE (http://ni.com/legal/termsofuse/unitedstates/us/).