9
Rosemount 248
August 2014
www.rosemount.com
Transmitter Specifications
Functional specifications
Inputs
User-selectable; sensor terminals rates to 42.4 Vdc. See
“Transmitter accuracy and ambient temperature effects” on
page 12 for sensor options.
Output
2-wire 4–20 mA, linear with temperature or input; digital output
signal superimposed on 4–20 mA signal, available for a Field
Communicator or control system interface.
Isolation
Input/output isolation tested to 500 Vac rms (707 Vdc) at 50/60
Hz.
Power supply
An external power supply is required for HART devices. The
transmitter operates on 12.0 to 42.4 Vdc transmitter terminal
voltage with load resistance between 250 and 1100 ohms. A
minimum of 17.75 Vdc power supply is required with a load of
250 ohms. Transmitter power terminals are rated to 42.4 Vdc.
Humidity limits
0–99% relative humidity, non-condensing
NAMUR recommendations
The 248 meets the following NAMUR recommendations:
NE 21 – Electromagnetic compatibility (EMC) for Process and
Laboratory Apparatus
NE 43 – Standard of the signal level breakdown information of
digital transmitters
NE 89 – Standard of temperature transmitters with digital
signal processing
Transient protection
The optional Rosemount 470 Transient Protector prevents
damage from transients induced by lightning, welding, heavy
electrical equipment, or switch gears. Refer to the 470 Product
Data Sheet (document number 00813-0100-4191) for
more information.
Temperature limits
Operating Limit
–40 to 85 °C (–40 to 185 °F)
Storage Limit
–50 to 120 °C (–58 to 248 °F)
Turn-on time
Performance within specifications in less than 5.0 seconds after
power is applied to transmitter, when damping value is set to
zero seconds.
Update rate
Less than 0.5 seconds
Damping
32 seconds maximum. 5 seconds default
Custom alarm and saturation levels
Custom factory configuration of alarm and saturation levels is
available with option code C1 for valid values. These values can
also be configured in the field using a Field Communicator.
Recommended minimum measuring span
10 K
Software detected failure mode
The values at which the transmitter drives its output in failure
mode depends on whether it is configured to standard, custom,
or NAMUR-compliant (NAMUR recommendation NE 43)
operation. The values for standard and NAMUR-compliant
operation are as follows:
Certain hardware failures, such as microprocessor failures, will
always drive the output to greater than 23 mA.
Maximum load = 40.8 x (supply voltage – 12.0)
4–20 mA dc
1322
1100
1000
750
500
250
0
1012.0 20
30
40
42.4
Load (Ohms)
Supply Voltage (Vdc)
Operating
Region
Figure 1. Operation Parameters
Standard
(1)
(1) Measured in milliamperes.
NAMUR NE43-
compliant
(1)
Linear Output 3.9 ≤ I ≤ 20.5 3.8 ≤ I ≤ 20.5
Fail High
21 ≤ I ≤ 23
(default)
21 ≤ I ≤ 23
(default)
Fail Low I ≤ 3.75 I ≤ 3.6
(2 pages)
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