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USB Voltmeter - 2 channel

This USB voltmeter has 2 independent differentials inputs. His A/D converter is galvanically separated from the boards. Thanks to this is measurement very stable and accurate. He includes a 24-bit A/D converter that allows high resolution even with large measurement range. He also includes EMI filter for RFI suppression. Galvanically isolated A/D converter is suitable for measuring devices that have different potential. Some devices can not be connected directly to a PC, therefore galvanic isolation is necessarily.
TCP voltmeter

USB Voltmeter features :

  • 24-bit A/D converter used
  • two differential inputs [ measures plus and minus voltage ]
  • driver installation is not necessary - it's plug & play device
  • works as a HID device [uses unique VID / PID number]
  • this voltmeter has excellent linearity and very low error.
  • supported OS: Windws XP, Win 7, Vista and Linux
  • API and source code for Windows and Linux
  • powered from the USB cable [ no external power supply ]
  • A/D converter is galvanically isolated from the board
  • logging data to a .csv file
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USB Voltmeter hardware

2-channel USB voltmeter consist of A/D converter and a microprocessor. They are connected via SPI bus. A/D converter is the type LTC2492, which is a 24-bit A/D converter. It can have 2 differential or 4 single-ended inputs. This USB voltmeter uses 2 differential inputs.
      To achieve very accurate measurements, a reference voltage source with a very low temperature coefficient was used. This USB voltmeter is galvanically isolated from the PC. Both channels must be connected independent. This is due to the internal structure of A/D converter. Block diagram of the voltmeter is shown in figure below.

Technical parameters

  • Size : 50 x 50 mm
  • input impedance : 1MOhm ( both channels )
  • Measured speed : 2 times/sec
  • Measured range : +/- 70 V DC
  • Resolution : 0,001 V
  • EMI filter
  • galvanically isolaion 4 kOhm
  • USB connector : type B

USB Voltmeter - pictures

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USB Voltmeter software

USB Voltmeter is supplied with software USBMeasure.exe. It is standard Windows aplication for communication with the USB Voltmeter. All the necessary files are in the installation package and software installation is easy.

API

We offer easy API for creation of custom applications. API contains all function to ensure measurement and data transfering to the PC via USB. API contains only several function and usage is very easy. Developer only call these functions and make their own graphical interface (GUI).

The API is implemented as a COM component (USBMeasure.dll). This component can be used in all known programming languages. It was tested with C#, C++, Visusal basic, Delphi and Javascript.

Linux

Linux also supported. The source code for Linux come from our users. We have not tested them but we assume that they work properly.

USB Voltmeter - HID device

USB voltmeters are HID devices (Human Interface Device). These devices use USB drivers already installed by default in Windows. It's the same type of communication as a PC communicates with the USB mouse or USB keyboard.

This applies to all versions of Windows - from windows XP above. USB voltmeters have their own unique VID & PID numbers, so there is no possibility of collision between other USB devices.

Screenshot
USBMeasure.exe software
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API usage - console aplication

using System.Collections.Generic;  using System.Text;   using System.Threading;
using USBMeasure;          // add reference to USBMeasure.dll

namespace 2channel
{
    class Program
    {   static void Main(string[] args)
        {
            CUSBMeasureMain usb = new CUSBMeasureMain();
            usb.USBMOpen();
            if (usb.Result == 0)
            {   Console.WriteLine("Unit type is: " + usb.UnitTypeText);    }
            else
                Console.WriteLine("USBMOpen  error : " + usb.Result);

            while (true)
            {   usb.USBMGetData();
                if (usb.Result == 0)
                    Console.WriteLine("Voltage : " + usb.UnitData.ToString("#000.00") + " Volt");
                    Console.WriteLine("Voltage2 : " + usb.UnitData2.ToString("#000.00") + " Volt");
                Thread.Sleep(400);
            }
            usb.USBMClose();
        }
    }
}
 
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Download software

2-channel USB voltmeter software ; [ Size : 25 kB ] :temp-thumb
USB voltmeter API ( USBMeasure.dll ) ; [ Size : 719 kB ] :temp-thumb
Source code for Windows ; [ Size : 124 kB ] : temp-thumb
Source code for Linux ; [ Size : 56 kB ] :temp-thumb
This software is only for 2-channel USB voltmeter. API ( USBMeasure.dll ) is common to all USB voltmeters.

If you want to make your own application, download and install USB voltmeter API. In the source code you will you find a simple applications that use this API.
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Data logging

USBMeasure.exe software allows you to store measurement data to .csv file. CSV file can be read in Microsoft Excel and other programs. For example csv file is here.

Accuracy

USB voltmeter has a simple design but achieves very high accuracy. She is almost like precision instruments. This table shows the measured values using 2-channel USB voltmeter and precision instruments Agilent U3401. (comming soon)
2-ch Voltmeter Agilent Error
x V x V 0.000 V
x V x V 0.000 V
x V x V 0.000 V
x V x V 0.000 V
x V x V 0.000 V
x V x V 0.000 V
x V x V 0.000 V
x V x V 0.000 V
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