Rockwell-automation T80004 Application Note Field Loop Configuration Uživatelský manuál stáhnout pdf (Strana 16)

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AN-T80004 Field Loop Configuration

Issue 10 Jun 13 AN-T80004 16

Digital Inputs

Thresholds

Digital inputs are essentially analogue inputs which are interpreted as digital. The voltage on the input

circuit is measured and allocated to an input state using thresholds, similar to analogue inputs above.

For digital inputs, the state bands are essential, since they define the digital input ‘off/open’ and

‘on/closed’ as well as line fault status. The thresholds are similar to analogue inputs except that they

operate over a wider voltage range. There are five configurable states separated by pairs of thresholds

for rising and falling state change. There are no THRSHIN and THRSHOUT boards to change the

thresholds online.

Typical

voltage

threshold

values

Input

Channel

State

Status

Line

Fault

Status

Over-range 7 False True

Tmax 36.00

False True

Short Circuit (approx 24V) 5

T8 22.00

4 or 5 False / False /

T7 21.00

True True

Contact Closed (approx 16V) 4 True False

T6 12.75

3 or 4 False / False /

T5 12.25

True True

Contact Indeterminate 3 False True

T4 11.75

2 or 3 False /

T3 11.25

True

Contact Open (approx 8V) 2 False False

T2 3.00

1 or 2 False /

T1 2.00

True

Open Circuit (approx 0V) 1 False True

Tmin -8.00

Under-range 7 False True

Thresholds are defined using a threshold template in the system configuration. Product description PD-

8082 describes how to edit threshold templates. The example above shows ‘Closed’ defined at

nominally 16 volts and ‘Open’ at nominally 8 volts, for a 24V digital input module. These are spaced

equally through the input voltage range, which allows broad voltage bands for each state.

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 55 56

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