Comparison | LabJack

By: Labjack  06-Dec-2011
Keywords: Analog Inputs

U3 compared to U12

The U3 is newer than the U12, and in general is faster, more flexible, and less expensive.

The U3 is about half the size of the U12. The enclosure can be mounted using a couple screws or DIN rail, whereas the U12 enclosure has no mounting options.

The U3 has up to 16 analog inputs compared to 8 on the U12. Any channel can be measured differentially versus any other channel. Accuracy specs are better than the U12.

The U3-LV has single-ended ranges of 0-2.4 or 0-3.6 volts, and a differential range of ±2.4 volts (pseudobipolar only). The U3-HV has 12 flexible I/O capable of those same low-voltage ranges, and 4 high-voltage analog inputs with a range of ±10 volts or -10/+20 volts. The U12 has a ±10 volt single-ended input range, and differential input ranges varying from ±20 volts to ±1 volt (all true bipolar). The circuitry used by the U12 to provide those high bipolar ranges is simple and inexpensive, but has drawbacks including relativity poor input impedance and errors which are different on every channel. There are many devices on the market now that have copied the same circuitry from the U12 and have the same drawbacks.

The U3 supports input streaming with a max rate of up to 50 ksamples/second, compared to 1.2 ksamples/second for the U12. The U3 achieves the full 12-bit resolution up to 2.5 ksamples/second, and then as speed increases the effective resolution drops to about 10 bits due to noise.

The U3 has 2 10-bit DACs as does the U12. The DACs on the U3 are derived from a regulated voltage, whereas the U12 DACs are derived from the power supply, so the U3 DACs will be more stable.

The digital I/O on the U3 use 3.3 volt logic, and are 5 volt tolerant. The U12 has 5 volt logic.

The U3 can have up to 2 timers and 2 counters. The timers have various functionality including period timing, duty cycle timing, quadrature input, pulse counting, or PWM output. The U12 has 1 counter and no timers.

The U3 has master support for SPI, I2C, and asynchronous serial protocols. The U12 does not support I2C, but does have some SPI and asynchronous support.

The U3 is supported on Windows, Linux, Mac OS X, and PocketPC. The U12 has full support for Windows, limited support for Linux, and limited public support for the Mac.

On Windows, the U3 uses the flexible UD driver which also works with the UE9. There is a specific separate driver for the U12.

The U3 is compatible with the LJTick signal conditioning modules, whereas the U12 is not. Current ticks include:

    .. versus UE9:

    The UE9 has all the same improvements as the U3 above, with the following additions and differences:

    The UE9 is about twice the size of the U3.

    The biggest difference is that the UE9 supports Ethernet communication in addition to USB. Ethernet communication uses standard TCP or UDP protocol, and supports Modbus/TCP. Ethernet speeds in command/response or stream mode are generally similar to USB speeds (see Sections 3.1 and 3.2 of the User's Guide for more information). The addition of an 802.11 WiFi bridge allows for inexpensive wireless data acquisition and control.

    When using Ethernet only (not USB), the UE9 has at least 500 volts of electrical isolation.

    The UE9 has 14 analog inputs and 2 analog outputs. The analog inputs and outputs on the UE9 have better accuracy, resolution, and linearity. The analog inputs are single-ended only, but the LJTick-InAmp can be used for low-level differential signals.

    Each analog input can be configured individually as unipolar (four ranges from 0-5 volts to 0-0.625 volts) or true bipolar (±5 volts). Analog input resolution is 12-bits at max speed (12 us conversion time), increasing up to 16-bits at slower speeds (2.7 ms conversion time).

    Maximum input stream rates range from 250 samples/second at 16-bit resolution to 50+ ksamples/second at 12-bit resolution. The UE9 has a very large 4 Mbit buffer for stream data, compared to a very small buffer on the U3.

    The UE9 has up to 6 timers available compared to 2 on the U3.

    The UE9-Pro has all the features of the normal UE9 with the addition of an auxiliary low-speed hi-resolution (24-bit) sigma-delta ADC. This converter takes about 125 ms per sample and provides an effective resolution of about 20-bits (18-bits noise free) over the 0-5 or ±5 volt ranges. Linearity and accuracy are also improved compared to the normal converter (which is still available on the UE9-Pro).

    .. versus U6:

    The U6 is similar to a UE9 without Ethernet, but the U6 is newer and has some analog input improvements.  Some key details:

    USB only.

    Up to 4 timers available.

    20 digital I/O (compared to 23 on the UE9).

    The U6/U6-Pro analog inputs have higher resolution than the UE9/UE9-Pro in most cases.

    Analog inputs are single-ended or differential, with input ranges of ±10, ±1, and ±0.1 volts.

    2 Fixed Current Outputs (200/10 μA).

Keywords: Analog Inputs