HyQuest Solutions iRIS 270, Руководство пользователя

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Installation
2.3.2.1 Analogue Inputs
The two analogue inputs are unit-polar 0-100mVdc, 0-5Vdc or 0-30Vdc with 16-bit resolution. Each input presents a load
impedance of 123.74 kΩ to the input signal.
Scaling factors should be chosen to convert from a raw value of, e.g. 0.0000 – 5.0000, which reflects the input signal
range of 0-5V. When current sources such as 0-20mA or 4-20mA are connected, an internal sink resistor (100 Ω) is
enabled by an internal user-settable link. In this mode the measured voltage range is 0-2V for a 0-20mA input and the
scaling factor should take this into account.
As the analogue inputs have an input impedance of 123.74 kΩ, the actual sink resistor impedance will be
slightly lower than the value fitted. When, for example, the current mode link is fitted, a sink resistor of 100
ohms is installed. The actual impedance will theoretically be 99.92 Ω; therefore, the voltage measured by the
iRIS will also be slightly lower than expected.
Figure 5 – Simplified Analogue Input Circuit
Figure 6 – Analogue Input / Output Links