myLab Precision Voltmeter with Current Limited Power Supply

High accuracy, low-noise, and seamless integration with 3rd party software makes myLab Precision Volt-meter with Power Supply an indispensable instrument in your laboratory and automated test environments (ATE). It is small and 10-times more cost effective than competitive instruments, suitable for multi-channel applications. Need a different function or a special function, then just select a another configuration.

Connections

Volt-meter input is available via Sensor Jack connector via three pins, and the 4th pin is the power supply.

  • System USB Ground (GND)
  • Voltage High Input Pin (High)
  • Voltage Low Input (Low)
  • Power Supply Output (Out) referred to Ground

Measurements are taken differentialy between the High and Low input terminals. To the Low terminal a selectable bias voltage can be applied in the range 0..4 V to be able to measure negative voltages.

../../_images/Voltmeter-Pinout.png

In isolated USB environment make sure that the GND terminal is connected to your target reference in the case of differential (balanced) measurements, or that Input.Low = Bias mode is used, to set the reference voltage potential.

CAUTION:
Make sure that Out is not connected to Low or High signals directly as Power Supply voltages can go as high as 23 V, while High and Low signals should stay within 5 V limits. If it is then pay extra attention not to configure the supply voltage amplitude above 5 V.

To remove noise we suggest to use a shielded cable, terminated to the GND pin at Jack side only, and a twisted pair for High and Low signals. An example of such cable represents a standard usb cable as shown below:

../../_images/usb-cable.jpg

Application Programming Interface

myLab Voltmeter programming interface is inspired by a Standard Commands for Programmable Instruments (SCPI). Commands, states, and readings are sorted in a structure as described in the following sub-sections. Values represented in italic format can only be read, not settable. Values in <…> are numerical values.

Measurements

Measure.Voltage = <value> [V]
Represents the latest voltage measurement. When Trigger.Source = Single then query this parameter to perform a conversion.
Measure.UTClock = <value> [ms]
Time-stamp of the Measurement.Voltage copied from the USB.UTClock at the time A/D sample is available.

Power Source

Source.Function.Shape = DC
Currently supported output is DC only.
Source.Function.Mode = Voltage
Currently supported mode is Voltage source.
Source.Voltage.Level.Immediate = <0..23> [V]
Sets the output voltage level immediatelly.
Source.Current.Limit.Amplitude = <0..0.5> [A]
Current limiter.

Input Options

Input.Type = Unbalanced | Balanced
Represents the input configuration, which is dependent on Input.Low settings. When Input.Low = Float, then Input.Type becomes Balanced, otherwise Unbalanced.
Input.Low = Float | Bias
Determines the potential of the low input connection, which can be floating or Biased by the Input.Bias value. When in Bias mode the Low input is connected to a Bias source via 17 kOhm resistance.
Input.Bias = <0..4080> [mV]
Determines the Bias voltage when Input.Low = Bias.

Sense Options

Sense.Voltage.Resolution = <20> [bits]
Determines the resolution in bits. Future versions will allow changing (reduction) of this parameter to gain more speed up to 10 kHz.
Sense.Voltage.Aperture = <value> [s]
Reflects the aperature time based on Sense.Voltage.NPLCycles settings. It cannot be entered.
Sense.Voltage.NPLCycles = AC1 | NotSynced
Determines the number of integration cycles. Currently supported is one AC cycle or not synced to the AC line frequency System.LFrequency.

Calculate Options

Calculate.Average.Count = <0..255>
Number of samples to average after A/D conversion (sensing).
Calculate.Average.TControl = Repeat
Clear average data and counter and restart the average process.
Calculate.Average.Type = Scalar
Averaging method currently supported.

Trigger Options

Trigger.Source = Immediate | Single
When Immediate system re-trigger immediately after conversion. When Single a Query request to Measure.Voltage triggers next conversion.

System Options

System.Reset = Ok | Reset | Bootloader
Determines the state or the last reset state. When Ok system started successfully. Setting to Reset will restart the system, and Bootloader option will enter the system upgrade mode.
System.Error = <errorCode>
Error reporting codes.
System.LFrequency = <50 | 60> [Hz]
Select the line frequency in conjunction with Sense.Voltage.NPLCycles.
USB.UTClock = <value> [ms]
A free running clock used to time-stamp measurements in the Measurements.UTClock.
myLab.VrefAccuracy = <0.10 | 0.02> %
Displays myLab voltage reference accuracy.

Voltmeter Specifications

Parameter min typ max Unit Notes
Voltage Measurement Range -0.1   Vusb-0.7 V Vusb is USB voltage (1)
Optional Output Reference 0.000   4.016 V  
Effective A/D Resolution   19.5   bits Differential Delta-Sigma
Voltage Resolution   11.7   uV One LSB
Measurement Accuracy 0.02 0.01   % Adjusted
Long Term Stability
  % TBD
Input Impedance   10   MOhm Balanced
Sample Rate at 16-bit     11000 sps To be supported in FW
Sample Rate at 18-bit     2400 sps To be supported in FW
Sample Rate (no AC rejection)   22 178 sps 178 to be supported in FW
Sample Rate (50 HZ rejection)     6.25 sps  
Sample Rate (60 HZ rejection)     7.5 sps  
Noise, N=1 (no averaging)   17   LSB Peak-to-Peak
Noise, N=2 (averaging)   14   LSB Peak-to-Peak
Noise, N=4 (averaging)   7   LSB Peak-to-Peak
Noise, N=10 (averaging)   5   LSB Peak-to-Peak

Notes:

  1. Extendable to 5 V by firmware.

Power Supply Specifications

Parameter min typ max Unit Notes
Power Supply Voltage Range 0   23 V  
Power Supply Current Range 0   500 mA Total power of 2 W
Output Resolution   20   mV  
Output Accuracy   50   mV  

Absolute Maximum Ratings

Stresses beyond these specifications may cause a harmful damage to the myLab.

Parameter min typ max Unit Notes
Voltage Measurement Range -0.5   Vusb+0.5 V Vusb is USB voltage
Optional Output Reference -0.5   Vusb+0.5 V  

New Features on the way

  • Power Supply Output Voltage and Current Measurements
  • Voltmeter Signal Attenuation for High Voltage Measurements
  • Voltmeter Programmable Input Gain Amplifier
  • Synchronous Triggering (Sampling) over Multiple myLabs
  • External Analog/Digital Trigger
  • Voltmeter Higher Sampling Rate at Reduced Resolution
  • Do you have a specific requirements?