Appendix A - Specifications [U12 Datasheet] | LabJack
« Close

Datasheets and User Guides

App Notes

Software & Driver


Appendix A - Specifications [U12 Datasheet]

Parameter Conditions Min Typical Max Units
USB Cable Length       3 meters
User Connection(s) Length CE compliance     3 meters
Supply Current (1)     20   mA
Operating Temperature   -40   85 °C
Clock Error ~ 25 °C     ±30 ppm
  0 to 70 °C     ±50 ppm
  -40 to 85 °C     ±100 ppm
+5 Volt Power Supply (+5V)          
Voltage (Vs) (2) Self-Powered 4.5   5.25 volts
  Bus-Powered 4.1   5.25 volts
Output Current (2) (3) Self-Powered 450   500 mA
  Bus-Powered 50   100 mA
Analog Inputs (AI0 - AI7)          
Input Range For Linear Operation AIx to GND, SE -10   10 volts
  AIx to GND, Diff. -10   30 volts
Maximum Input Range AIx to GND -40   40 volts
Input Current (4) Vin = +10 volts   70.1   µA
  Vin = 0 volts   -11.7   µA
  Vin = -10 volts   -93.5   µA
Resolution (No Missing Code) C/R and Stream   12   bits
  Burst Diff. (5)   12   bits
  Burst SE (5)   11   bits
Offset G = 1 to 20   ±1 * G   bits
Absolute Accuracy SE   ±0.2 ±0.4 % FS
  Diff.   ±1   % FS
Noise C/R and Stream   ±1   bits
Integral Linearity Error     ±1   bits
Differential Linearity Error     ±0.5   bits
Repeatability     ±1   bits
CAL Accuracy CAL = 2.5 volts   ±0.05 ±0.25 %
CAL Current Source     1 mA
  Sink 20 100   µA
Trigger Latency Burst 25   50 µs
Trigger Pulse Width Burst 40     µs
Analog Outputs (AO0 & AO1)          
Maximum Voltage (6) No Load   Vs   volts
  At 1 mA   0.99 * Vs   volts
  At 5 mA   0.96 * Vs   volts
Source Impedance     20   Ω
Output Current Each AO     30 mA
Low Level Input Voltage       0.8 volts
High Level Input Voltage   3   15 volts
Input Leakage Current (7)     ±1   µA
Output Short-Circuit Current (8) Output High   3.3   mA
Output Voltage (8) No Load Vs - 0.4 Vs   volts
  At 1 mA   Vs - 1.5   volts
Series Impedance (8)     1500   Ω
Low Level Input Voltage (9) D0 - D12     0.8 volts
  D13 - D15     1 volts
High Level Input Voltage (9) D0 - D12 2   Vs + 0.3 volts
  D13 - D15 4   Vs + 0.3 volts
Input Leakage Current (7)     ±1   µA
Output Current (9) Per Line     25 mA
  Total D0-D15     200 mA
Output Low Voltage       0.6 volts
Output High Voltage   Vs - 0.7     volts
Series Impedance (9) Output-High   80   Ω
  Output-Low   30   Ω
Low Voltage (10)   GND   1 volts
High Voltage (10)   3   15 volts
Schmitt Trigger Hysteresis     20-100   mV
Input Leakage Current (7)     ±1   µA
Minimum High Time       500 ns
Minimum Low Time       500 ns
Maximum Input Frequency   1     MHz
(1) Current drawn by the LabJack through the USB. The status LED is responsible for 4-5 mA of this current. 
(2) Self-powered would apply to USB hubs with a power supply, all known desktop computer USB hosts, and some notebook computer USB hosts. Bus-powered would apply to USB hubs without a power supply and some notebook computer USB hosts. 
(3) This is the total current that can be sourced by +5V, analog outputs, and digital outputs. 
(4) The input current at each analog input is a function of the voltage at that input (Vin) with respect to ground and can be calculated as: (8.181*Vin - 11.67) μA. 
(5) Single-ended burst mode only returns even binary codes, and thus has a net resolution of 11 bits. In addition, extra noise in burst mode can reduce the effective resolution. 
(6) Maximum analog output voltage is equal to the supply voltage at no load. 
(7) Must also consider current due to 1 MΩ resistor to ground. 
(8) The IO lines each have a 1500 ohm series resistor. 
(9) The D lines have no series resistor. It is up to the user to make sure the maximum voltages and currents are not exceeded.  The internal transistors do have some inherent resistance as specified above. 
(10) CNT is a Schmitt Trigger input. 


How about putting the GENDER of the D25 on your literature somewhere please, I can't find it ANYWHERE?

Also, If I use pull-up's on the D0-d15 I/O's will that take them to 5V? if so why did you not enable the internal PU's on the PIC core on these ports? Would make life a WHOLE lot easier.

You are right.  I am having trouble finding that the DB25 connector is female, and can't even find any pictures showing the connector.  Will add that.

The digital lines have 1M pull-downs, so you can use stronger pull-ups to another voltage if you want.  Have you considered the newer U3?  See the comparison.

I don't recall why the U12 does not use the PIC pull-ups.  Seems like there was a reason, but will have to dig through the PIC datasheet to try and remember.


Thanks for the prompt reply - TOP MARKS ;-)

Looking at the pins on the type of PIC you used to make the U12, it's probably because this would have affected other functionality.

Nonetheless a command to switch the internal pull-ups on or off could be useful for future reference.

Looks like only PortB has pull-up capability, which is D8-D12.  I suspect the biggest factor, then, might have been that we wanted everything to behave the same (whenever possible) so just decided we would add pull-ups or pull-downs externally.

The reason for pull-downs was likely that the U12 design was largely motivated by student labs at colleges and universities, and we thought students would like to see a low on unconnected digital inputs.  These days, we use pull-ups on all our devices which seems to be more industry standard with digital logic.


I am looking for the input capacitance of the analogue inputs.

I am considering adding an op amp buffer at the inputs and the capacitance could affect the stability.

See page 11 and 12 of

First you go through ~100k of resistance, then there is ~10pF of capacitance.  The resistance should decouple your amp so you should not have to worry about it.

what will happen if the max current of the anolog output goes more than 30 mA?

Thank you for your replay.

The problem which i have now:  

I use a U12 Anolog output to give a 0-5V signal to a motor controller as a pedal signal (and i connected the U12 GND with the controller GND). But U12 seems not so stable, the voltage from U12 is intermittent and the green LED turns on and off intermittently. And the result is that the motor runs for several seconds(not more than 10 seconds) and stop for about 3-5 seconds. I thought the problem is because of my laptop before, then i changed to a normal desk PC, but still the same problem. I used multimeter to measure the output voltage from the anolog output port, it acts the same way like the motor... do you have any idea about this problem? Is that because of the current? Or some other kind interference? look forward to your reply. thank you 

If you remove the connections to the motor controller, so the U12 just has USB connected, does the problem go away?

Sorry for replying so late.

Yes, the problem goes away if i disconnected the labjack U12 from the motor controller.

and i have one more question mow, i have two gear tooth sensors which output pulses signals, but U12 only has one counter. So is that possible to count the two signals successfully(with matlab), i mean "at the same time"? Or i have to buy another labjack, maybe like U3 which has two counters?

Thank you in advance. 


It seems then that something about the connections to the motor controller is causing a problem.  Perhaps the motor controller is drawing too much current from AO0?  If you need further troubleshooting help I suggest you start a topic on our forum, including a link to details for the motor controller and a listing of the connections between the U12 and the controller.

If the 2nd signal is quite slow, say less than 20 Hz, you might be able to count it by simply polling a digital input and counting in software.  Otherwise, you are correct that the U3 (or any of our other devices) would be a better solution for you.

I guess that the problem is because the motor controller is drowing too much current from AO0. But the strange thing is that it works normally sometimes... that's what i can't understand... 

The 2nd signal is also quite fast...gear tooth... much more than 20Hz. So i guess i need to buy a U3 maybe.

Anyway, thank you very much.


I have 6nos analog input 4-20mA signal 

how it work