Omega OM-USB-TEMP-AI, Руководство пользователя

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OM-USB-TEMP-AI User's Guide Specifications
23
Channel configurations
Table 2. Channel configuration specifications
Channel Category Conditions Max number of
sensors (all channels
configured alike)
T0x-T3x Disabled All temperature input channels are disconnected from screw
terminals and internally connected to GND.
See Note 4
T0x-T3x Thermocouple
(Note 1)
4 differential channels
T0x-T3x Semiconductor
sensor (Note 1)
4 differential channels
2-wire input configuration with a single sensor per channel
pair
2 differential channels
2-wire input configuration with two sensors per channel pair 4 differential channels
3-wire configuration with a single sensor per channel pair 2 differential channels
4-wire input configuration with a single sensor per channel
pair
2 differential channels
T0x-T3x RTD and
Thermistor
(Note 1)
4-wire input configuration with two sensors per channel pair 4 differential channels
V0x-V3x Disabled All voltage input channels are disconnected from screw
terminals and internally connected to GND.
See Note 4
V0x-V3x Differential
(Note 2)
4 differential channels
V0x-V3x Single-ended 4 single-ended channels
Note 1:
Internally, the OM-USB-TEMP-AI has four, dual-channel, fully differential A/Ds providing a
total of eight input channels. The temperature input channels are configured as two channel pairs
with T0x/T1x and T2x/T3x accepting temperature sensor type inputs. This "channel-pairing"
requires T0x/T1x, and T2x/T3x to be configured to monitor the same category of temperature
sensor. Mixing different sensor types of the same category (such as a type J thermocouple on
temperature channel 0 and a type T thermocouple on temperature channel 1) is valid.
Note 2:
The voltage input channels, channels V0x, V1x, V2x, and V3x are not configured as channel
pairs. Therefore each channel can be configured independently. When connecting differential
inputs to floating input sources, you must provide a DC return path from each differential input to
ground. To do this, simply connect a resistor from each of the differential inputs to GND. A
value of approximately 1Meg ohm can be used for most applications.
Note 3:
Channel configuration information is stored in the EEPROM of the isolated microcontroller by
the firmware whenever any item is modified. Modification is performed by commands issued
over USB from an external application, and the configuration is made non-volatile through the
use of the EEPROM.
Note 4:
The factory default configuration is
Disabled
. The Disabled mode disconnects the temperature
and voltage inputs from the terminal blocks, and internally connects ground (GND) to all of the
A/D inputs. This mode also disables each of the current excitation sources.