Measuring Accuracy; Reference Conditions According To Iec 60770; Dynamic Response (According To Iec 61298-1); Measuring Error For Setting Cut-Off Point - ABB 261GS Operating Instruction

9.3

Measuring accuracy

9.3.1

Reference conditions according to IEC 60770

— Ambient temperature TU = constant in the range
18 ... 30 °C (64 ... 86 °F)
— Humidity r.F = constant, in the range 30 ... 80 %
— Ambient pressure PU = constant in the range
950 ... 1,060 mbar.
— Measuring span based on zero point
— Transmitter with separating diaphragm or Hastelloy
— Filling fluid: silicone oil
— Supply voltage: 24 V DC
— Load with HART: 250 Ω
— Transmitter not grounded
— Characteristic curve setting: linear, 4 ... 20 mA.
Unless otherwise stated, errors are specified as a % of the
measuring span value.
The accuracy of the measurement in relation to the upper
range limit (URL) is affected by the turndown (TD); i.e., the
ratio of the upper range limit (URL) to the set span (URL/span).
FOR OPTIMUM MEASURING ACCURACY, IT IS
RECOMMENDED THAT YOU SELECT THE SENSOR CODE
WHICH WILL PROVIDE THE LOWEST TD VALUE.
9.3.2

Dynamic response (according to IEC 61298-1)

Reaction time
Time constant (63.2 % of total step
response)
9.3.3

Measuring error for setting cut-off point

Turndown
1:1 ... 10:1
>10:1
9.3.4

Ambient temperature

Thermal change in ambient temperature as regards the zero
signal and span (turndown up to 6:1), in relation to the set
span
Temperature range
-10 ... 60 °C (14 ... 140 °F)
-40 ... -10 °C (-40 ... 14 °F)
60 ... 85 °C (140 ... 185 °F)
40 IM/261Gx/Ax-EN Rev. 08 | 261Gx, 261Ax
100 ms
150 ms
Measuring error
±0.1 %
± (0.1 + 0.005 x TD - 0.05) %
Maximum effect on zero signal
and span
All measuring ranges
± (0.2 % x TD + 0.2 %)
All measuring ranges
±((0.1 % / 10 K) x TD + (0.1 / 10K))
9.3.5 Temperature coefficient (T
Effect of the ambient temperature per 10 K (but limited to the
maximum effect of the temperature change, see previous
information). The information refers to the set measuring span.
Temperature range
-10 ... 60 °C (14 ... 140 °F)
9.3.6

Power supply

Within the specified limits for the voltage / load, the total
influence is less than 0.001 % of the upper measuring range
limit per volt.
9.3.7

Load

Within the specified load / voltage limits, the total influence is
negligible.
9.3.8

Electromagnetic fields

Total influence is less than 0.3 % of measuring span from
80 ... 1,000 MHz and for field strengths up to 10 V/m when
tested with unshielded conduit, with or without meter.
9.3.9

Mounting position

Nominal position: vertical; process connection at bottom.
Mounting position deviant from the standard position influence
the output due to the filling liquid. With a deviation of 90° from
standard position the effect is 1.12 mbar + 0.01 mbar/10K.
This effect can be compensated by carrying out zero signal
adjustment and configuring the mounting angle with the LCD
indicator or DTM.

9.3.10 Long-term stability

±(0.10 x TD) % / year

9.3.11 Vibration effect

±(0.10 x TD) % acc. to IEC 61298-3
)
k
Effect on zero signal and span
Sensor code C, F:
± (0.15 % x TD + 0.15 %)
Sensor code L, D, U, R, V:
± (0.05 % x TD + 0.05 %)