14.0 Analog Inputs [T-Series Datasheet]

Figure 14.0-1 T4 Dedicated Analog Inputs

Figure 14.0-2 T4 Flexible I/O

The LabJack T4 has up to 12 built-in analog inputs, readable as AIN0-AIN11:

• AIN0-AIN3 are dedicated ±10 volt inputs:
  • Available on screw terminals AIN0-AIN3.
  • Always ±10 volt analog inputs.
• AIN4-AIN7 are flexible 0 to +2.5 volt inputs:
  • Available on screw terminals FIO4-FIO7.
  • Configurable to be digital inputs/outputs.  See "Flexible I/O" below.
• AIN8-AIN11 are flexible 0 to +2.5 volt inputs:
  • Available on the DB15 connector.
  • Configurable to be digital inputs/outputs. See "Flexible I/O" below.

T4 AIN Channel Registers

Name	Start Address	Type	Access
AIN#(0:11)	0	FLOAT32	R
AIN#(0:11) - Starting Address: 0 Returns the voltage of the specified analog input. Data type: FLOAT32  (type index = 3) Read-only This register may be streamed Expanded Names Addresses AIN0, AIN1, AIN2, AIN3, AIN4, AIN5, AIN6, AIN7, AIN8, AIN9, AIN10, AIN11 Show All 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 Show All

Figure 14.0-3 T7 Analog Inputs

The LabJack T7 has 14 built-in analog inputs, readable as AIN0-13:

• AIN0-AIN3 are available on the screw terminals and on the DB37 connector. See "Duplicated Terminals" below.
• AIN4-AIN13 are available only on the DB37 connector.

T7 AIN Channel Registers

Name	Start Address	Type	Access
AIN#(0:13)	0	FLOAT32	R
AIN#(0:13) - Starting Address: 0 Returns the voltage of the specified analog input. Data type: FLOAT32  (type index = 3) Read-only This register may be streamed Expanded Names Addresses AIN0, AIN1, AIN2, AIN3, AIN4, AIN5, AIN6, AIN7, AIN8, AIN9, AIN10, AIN11, AIN12, AIN13 Show All 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 Show All

In addition to the 14 built-in analog inputs, the T7 has special and extended channels.

• • AIN14 is internally connected to an internal temperature sensor.
  • AIN15 is internally connected to GND.  Useful for measuring noise or looking at offset error.
  • AIN16-AIN47 are optional extended channels that can be created with custom analog input muxing circuitry. See Section 14.2 Extended Channels for more information.
  • AIN48-AIN127 are extended channels that are available when using a Mux80.

T7 Extended AIN Channel Registers

Name	Start Address	Type	Access
AIN#(48:127)	96	FLOAT32	R
AIN#(48:127) - Starting Address: 96 Returns the voltage of the specified analog input. Data type: FLOAT32  (type index = 3) Read-only This register may be streamed Expanded Names Addresses AIN48, AIN49, AIN50, AIN51, AIN52, AIN53, AIN54, AIN55, AIN56, AIN57, AIN58, AIN59, AIN60, AIN61, AIN62, AIN63, AIN64, AIN65, AIN66, AIN67, AIN68, AIN69, AIN70, AIN71, AIN72, AIN73, AIN74, AIN75, AIN76, AIN77, AIN78, AIN79, AIN80, AIN81, AIN82, AIN83, AIN84, AIN85, AIN86, AIN87, AIN88, AIN89, AIN90, AIN91, AIN92, AIN93, AIN94, AIN95, AIN96, AIN97, AIN98, AIN99, AIN100, AIN101, AIN102, AIN103, AIN104, AIN105, AIN106, AIN107, AIN108, AIN109, AIN110, AIN111, AIN112, AIN113, AIN114, AIN115, AIN116, AIN117, AIN118, AIN119, AIN120, AIN121, AIN122, AIN123, AIN124, AIN125, AIN126, AIN127 Show All 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 166, 168, 170, 172, 174, 176, 178, 180, 182, 184, 186, 188, 190, 192, 194, 196, 198, 200, 202, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244, 246, 248, 250, 252, 254 Show All

Flexible I/O are I/O ports that may be configured as analog inputs, or as digital inputs or outputs.

Flexible I/O Configuration

Name	Start Address	Type	Access
DIO_INHIBIT	2900	UINT32	R/W
DIO_INHIBIT - Address: 2900 A single binary-encoded value where each bit determines whether _STATE, _DIRECTION or _ANALOG_ENABLE writes affect that bit of digital I/O. 0=Default=Affected, 1=Ignored. Data type: UINT32  (type index = 1) Readable and writable Default value: 0 Constant Value Affected 0 Ignored 1
DIO_ANALOG_ENABLE	2880	UINT32	R/W
DIO_ANALOG_ENABLE - Address: 2880 Read or write the analog configuration of all digital I/O in a single binary-encoded value. 1=Analog mode and 0=Digital mode. When switching from analog to digital, the lines will be set to input. Writes are filtered by the value in DIO_INHIBIT. Data type: UINT32  (type index = 1) Readable and writable Constant Value Digital mode 0 Analog mode 1

AIN4-AIN11 are flexible I/O. To configure these channels as analog inputs:

• Set the correct bit of DIO_INHIBIT to 0
• Set the correct bit of DIO_ANALOG_ENABLE to 1

The bit to set of DIO_INHIBIT and of DIO_ANALOG_ENABLE is the same as the channel number. For example, to configure AIN4 (screw terminal FIO4) as an analog input:

• Set bit 4 of DIO_INHIBIT to 0
• Set bit 4 of DIO_ANALOG_ENABLE to 1

AIN0-AIN3 are dedicated analog inputs and cannot be configured as digital I/O.

Note that simply doing an analog read on AIN4-AIN11 automatically configures that line (FIO4-EIO3) as analog, so few people use the 2 registers mentioned above.  See "Flexible I/O Auto-Configuration" in Section 13.1 Flexible I/O.

Single-ended AIN readings are read with ground (GND) as a reference point. Differential readings use a second AIN as a reference point. For more, see the Differential Readings App Note.

Negative Channel Registers

Name	Start Address	Type	Access
AIN#(0:13)_NEGATIVE_CH	41000	UINT16	R/W
AIN#(0:13)_NEGATIVE_CH - Starting Address: 41000 Specifies the negative channel to be used for each positive channel. 199=Default=> Single-Ended. Data type: UINT16  (type index = 0) Readable and writable Default value: 199 T7: For base differential channels, positive must be even channel from 0-12 and negative must be positive+1. For extended channels 16-127, see Mux80 datasheet. Expanded Names Addresses AIN0_NEGATIVE_CH, AIN1_NEGATIVE_CH, AIN2_NEGATIVE_CH, AIN3_NEGATIVE_CH, AIN4_NEGATIVE_CH, AIN5_NEGATIVE_CH, AIN6_NEGATIVE_CH, AIN7_NEGATIVE_CH, AIN8_NEGATIVE_CH, AIN9_NEGATIVE_CH, AIN10_NEGATIVE_CH, AIN11_NEGATIVE_CH, AIN12_NEGATIVE_CH, AIN13_NEGATIVE_CH Show All 41000, 41001, 41002, 41003, 41004, 41005, 41006, 41007, 41008, 41009, 41010, 41011, 41012, 41013 Show All
AIN_ALL_NEGATIVE_CH	43902	UINT16	R/W
AIN_ALL_NEGATIVE_CH - Address: 43902 A write to this global parameter affects all AIN. Writing 1 will set all AINs to differential. Writing 199 will set all AINs to single-ended. A read will return 1 if all AINs are set to differential and 199 if all AINs are set to single-ended. If AIN configurations are not consistent 0xFFFF will be returned. Data type: UINT16  (type index = 0) Readable and writable Default value: 199 T7: Minimum firmware version: 0.9328

The AIN#(0:13)_NEGATIVE_CH and AIN_ALL_NEGATIVE_CH parameters configure whether the AIN performs differential vs. single-ended readings (not to be confused with bipolar and unipolar—the T7 is always bipolar).

Example:

To take a differential reading on AIN2, set AIN3 as its negative channel (AIN2-AIN3):

1. 1. Write 3 to AIN2_NEGATIVE_CH (address 41002)
   2. Read AIN2

To read AIN2 single-ended again (AIN2-GND):

1. 1. Write 199 to AIN2_NEGATIVE_CH (address 41002)
   2. Read AIN2

Built-in AIN

For AIN0 through AIN13, differential channels are adjacent even/odd pairs such that the positive channel is even and the negative channel is greater than the positive channel by 1. Odd channels, such as AIN3_NEGATIVE_CH (address 41003), should not be written to because only an even channel can have an associated negative channel.

Temperature and Ground

AIN14 is the internal temperature sensor and AIN15 is GND. Neither can be read differentially.

Extended AIN

For AIN16 and greater, the rules for pairing differential channels is different. See 14.2 Extended Channels or the Mux80 datasheet for more.

T7 Internal Amplifier: The analog inputs are connected to a high-impedance instrumentation amplifier, as shown in Figure 4.2-2. This in-amp does the following:

• Buffers the signal for the internal ADCs
• Allows for single-ended or differential conversions
• Provides gains of x1, x10, x100, and x1000 (corresponding to ranges of ±10V, ±1V, ±0.1V, and ±0.01V, respectively).

Range Registers

Name	Start Address	Type	Access
AIN#(0:13)_RANGE	40000	FLOAT32	R/W
AIN#(0:13)_RANGE - Starting Address: 40000 The range/span of each analog input. Write the highest expected input voltage. Data type: FLOAT32  (type index = 3) Readable and writable Default value: 0 T7: Valid values/ranges: 0.0=Default=> +/-10V, 10.0=> +/-10V, 1.0=> +/-1V, 0.1=> +/-0.1V, or 0.01=> +/-0.01V. T4: Valid values/ranges: 0.0=Default=> 0-2.5 V on LV lines and ±10 V on HV lines. Expanded Names Addresses AIN0_RANGE, AIN1_RANGE, AIN2_RANGE, AIN3_RANGE, AIN4_RANGE, AIN5_RANGE, AIN6_RANGE, AIN7_RANGE, AIN8_RANGE, AIN9_RANGE, AIN10_RANGE, AIN11_RANGE, AIN12_RANGE, AIN13_RANGE Show All 40000, 40002, 40004, 40006, 40008, 40010, 40012, 40014, 40016, 40018, 40020, 40022, 40024, 40026 Show All
AIN_ALL_RANGE	43900	FLOAT32	R/W
AIN_ALL_RANGE - Address: 43900 A write to this global parameter affects all AIN. A read will return the correct setting if all channels are set the same, but otherwise will return -9999. Data type: FLOAT32  (type index = 3) Readable and writable Default value: 0 T7: Minimum firmware version: 0.9328

Example:

If the voltage source connected to AIN1 has a known range of 0 to 0.7V, the appropriate range for AIN1 is the ±1V range. To read AIN1 with the ±1V range:

1. 1. Write 1.0 to AIN1_RANGE (address 40002)
   2. Read AIN1

The range registers (AIN#(0:13)_RANGE and AIN_ALL_RANGE) control the gain of the T7's internal instrumentation amplifier. The in-amp supports gains of x1, x10, x100, and x1000.

Values written to RANGE are rounded up (except for values greater than 10.0, which are rounded down). For example, writing 0.5 to AIN_ALL_RANGE will set the analog input range to ±1 volts.

The T7 knows what the internal gain is set to and adjusts the return values to give the voltage at the input terminals, so if you connect a 0.8 volt signal to the input terminals, it will be amplified to 8.0 volts before being digitized, but the reading you get back will be 0.8 volts.

AIN0-AIN3 appear on the built-in screw-terminals and also on the DB37 connector. Users should only connect to one or the other, not both at the same time.

To prevent damage due to accidental short circuit, both connection paths have their own series resistor. All AIN lines have a 2.2k series resistor, and in the case of AIN0-AIN3 the duplicated connections each have their own series resistor, so if you measure the resistance between the duplicate terminals you will see about 4.4k.