IC-GD Datasheet, PDF (29/55 Pages) IC-Haus GmbH – UNIVERSAL I/O INTERFACE

iC-GD
UNIVERSAL I/O INTERFACE
preliminary
Rev A1, Page 29/55
read back via the SPI (X_meas). The two maximum val-
ues are used for all measuring ranges (value 1 and 2).
In addition, for the symmetric measuring ranges, the off-
set at 0 V/0 mA (value 0) is determined. For the current
measurement offset, also the current chip temperature
and the temperature coefficient values AITKQ, AITKL
are required. The latter are stored on the chip, see table
17. The required values are used unitless in the format
of the process data: X_set und X_meas as signed numbers,
and additionally for the current measurement AITKQ,
AITKL and CHIP_TEMP, all as unsigned numbers.
The following four conditions must be kept:
AGFnx
1.5 + ₂₁₅
∗ AOFnx + 2¹⁵ > 2¹⁵ − 1
AGFnx
1.5 + ₂₁₅
∗ AOFnx − 2¹⁵ < −2¹⁵
AGFnx
1.5 + ₂₁₅
∗ AOFnx < 2¹⁵ − 1
AGFnx
1.5 + ₂₁₅
∗ AOFnx > −2¹⁵
3-point calibration (symmetrical ranges)
The following formulae are valid for the ranges ±10 V,
±1 V, ±100 mV, ±10 mV, ±20 mA.
Point 0 is calibrated exactly (to use for offset), point 1
and point 2 are calibrated best possible. The points
should be distributed equidistantly.
Example
Point 0: 0 V, point 1: +10 V, point 2: -10 V.
AGFnx =
X _{set 1} − X _{set 0 +} X _{set 2} − X _{set 0 − 3 ∗ 214}
X _{meas 1} − X _{meas 0} X _{meas 2} − X _{meas 0}
AOFnx_(VI) =
X _{set 0}
1.5
+
AGFnx
215
− X _{meas 0}
AOFnx_(CI) =
X _{set 0}
1.5
+
AGFnx
215
− X _{meas 0}
1
∗
f_T
2-point calibration (asymmetrical ranges)
The following formulae are valid for the ranges -17.5 mV
to 87.5 mV, -4.375 mV to 21.875 mV, 4 to 20 mA. Point
1 and point 2 are to be adjusted exactly.
Example
Point 1: 4 mA, point 2: 20 mA.
AGFnx =
X _{set 2} − X _{set 1 − 1.5 ∗ 215}
X _{meas 2} − X _{meas 1}
AOFnx_(VI)
=
X _{set 1}
∗ X _{meas 2}
X _{set 2}
− X _{set 2}
− X _{set 1}
∗
X _{meas 1}
AOFnx_(CI)
=
X _{set 1}
∗ X _{meas 2}
− X _{set 2}
∗
X _{meas 1} + c₀ ∗ (f _T − 1) ∗ (X _{set 2}
(X _{set 2} − X _{set 1}) ∗ f _T
− X _{set 1}
+ X _{meas 1}
− X _{meas 2})
AITKL ∗ CHIP_TEMP AITKQ ∗ CHIP_TEMP²
with c₀ = 7710, f _T = 1 +
2¹⁸
−
2²²