Channel Numbers - LabJack UE9 User Manual

to consider one common ground (GND).
See the AIN, DAC, and Digital I/O Sections for more information about grounding.
2.6 - Vs
The Vs terminals are designed as outputs for the internal supply voltage (nominally 5 volts). This will be the voltage provided from
the USB connection (Vusb) or an external power supply (Vext) as described in Section 2.3. The Vs connections are outputs, not
inputs. Do not connect a power source to Vs. All Vs terminals are the same.
2.7 - AIN
The LabJack UE9 has 14 user accessible analog inputs built-in. All the analog inputs are available on the DB37 connector, and
the first 4 are also available on the built-in screw terminals.
The analog inputs have variable resolution, where the time required per sample increases with increasing resolution. The value
passed for resolution is from 0-17, where 0-12 all correspond to 12-bit resolution, and 17 still results in 16-bit resolution but with
minimum noise. The UE9-Pro has an additional resolution setting of 18 that causes acquisitions to use the alternate high-
resolution converter (24-bit sigma-delta). Resolution is configured on a device basis, not for each channel.
The analog inputs are connected to a high impedance input buffer. The inputs are not pulled to 0.0 volts, as that would reduce the
input impedance, so readings obtained from floating channels will generally not be 0.0 volts. The readings from floating channels
depend on adjacent channels and sample rate. See Section 2.7.3.8.
When scanning multiple channels, the nominal channel-to-channel delay is specified in Appendix A, and includes enough settling
time to meet the specified performance. Some signal sources could benefit from increased settling, so a settling time parameter
is available that adds extra delay between configuring the multiplexers and acquiring a sample. The passed settling time value is
multiplied by 5 microseconds to get the approximate extra delay. This extra delay will impact the maximum possible data rates.

2.7.1 - Channel Numbers

The LabJack UE9 has 16 total built-in analog inputs. Two of these are connected internally (AIN14/AIN15), leaving 14 user
accessible analog inputs (AIN0-AIN13). The first 4 analog inputs, AIN0-AIN3, appear both on the screw terminals and on the DB37
connector. These connections are electrically the same, and the user must exercise caution only to use one connection or the
other, and not create a short circuit.
Following is a table showing the channel number to pass to acquire different readings from the internal channels (AIN14/15).
Channel#
14 Vref (~2.43 V)
128 Vref (~2.43 V)
132 Vsupply
133 Temp Sensor
15 GND
136 GND
140 Vsupply
141 Temp Sensor
Table 2.7.1-1. Internal Channels
GND and Vref connect 0.0 volts and about 2.43 volts to the internal channels. These signals come through the same input path as
channels 0-13, and thus can be used to test various things.
Vsupply connects the 5 volt supply voltage (Vs) directly to the analog to digital converter through a voltage divider that attenuates it
by 40%. The attenuation of this voltage divider is not measured during the UE9 factory calibration, but the accuracy should typically
be within 0.2%. Note that a reading from this channel returns Vs during the execution of the command, and Vs might dip slightly
while increasing a command due to the increased current draw of the UE9, thus this reading might be slightly lower than a
comparative reading from an external DMM which averages over a longer time.
The channels with the same names are identical. For instance, channel 133 or 141 both read the same internal temperature
sensor. See Section 2.7.4 for information about the internal temperature sensor.
The Mux80 accessory uses multiplexer ICs to easily expand the total number of analog inputs available from 14 to 84, or you can
connect multiplexer chips yourself.
The DB37 connector has 3 MIO lines designed to address expansion multiplexer ICs (integrated circuits), allowing for up to 112
total external analog inputs. The MAX4051A (maxim-ic.com) is a recommended multiplexer, and a convenient ±5.8 volt power
supply is available so the multiplexers can pass bipolar signals (see Vm+/Vm- discussion in Section 2.12). Note that the EB37
experiment board accessory is a convenient way to connect up to 7 MAX4051A multiplexer chips, but the UE9s ±5.8 volt supply
should still be used to power the chips as the ±10 volt supply on the EB37 is beyond the rating of the MAX4051A. Figure 2-2
shows the typical connections for a pair of multiplexers.
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