PCE Instruments PCE-SCI-L handleiding

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Handleiding

PCE Instruments

10. Input signals

10.1 Load cell signals

Table 12 | Connection example for load cell signals

123

Vexc -

mV -

sense -

456

Vexc +

mV +

sense +

MEASURING LOAD CELL SIGNALS

The instrument can be congured to measure load cell

signals, with pre-congured ranges from 0/5 mV up to

0/80 mV. The instrument provides excitation voltage of

+5 Vdc to power the load cell, with a maximum of 70 mA

(this is 4 standard load cells of 350 Ohms). Bipolar ranges from ±5 mV

up to ±80 mV can also be congured.

‘SENSE’ FUNCTION

The instrument reads the actual excitation voltage received by the load

cell, and compensates the signal read for any variations of the excitation

voltage. The applied voltage is read through the ‘sense’ wires and the

‘sense’ wires must be connected to the load cell. If it is not possible to

connect the ‘sense’ wires to the load cell, apply a shortcircuit between

terminals ‘sense +’ and ‘Vexc +’ (terminals 5 and 4), and between terminals

‘sense -’ and ‘Vexc -’ (terminals 2 and 1). (see section 7.2).

PREDEFINED CONFIGURATION CODES

See ‘Table 13’ for a list of predened input-output conguration codes.

To activate a code see section 13.1.

CUSTOMIZED SIGNAL RANGES

To customize the input and / or output signal ranges, access the

‘Advanced scaling’ menu (see section 13.4).

MAXIMUM OVERSIGNAL AND PROTECTIONS

‘Maximum oversignal’ is the maximum signal accepted by the instrument.

Higher signal values may damage the instrument. Lower signal values

are non destructive but may be out of accuracy specications. Do not

connect active signals to the excitation voltage terminals.

OUTPUT SIGNAL

The output signal is congurable to 4/20 mA (active and passive) and

0/10 Vdc.

Table 13 | Input signal ranges for load cell signals

Input

range

Code for

4/20 mA output

Code for

0/10 Vdc output

Accuracy

(% FS)

Max.

oversignal

Zin

0/5 mV

010 110 <0.15 % ±12 Vdc 20 MOhm

0/10 mV 011 111 <0.10 % ±12 Vdc 20 MOhm

0/15 mV 012 112 <0.10 % ±12 Vdc 20 MOhm

0/20 mV 013 113 <0.10 % ±12 Vdc 20 MOhm

0/25 mV 014 114 <0.10 % ±12 Vdc 20 MOhm

0/30 mV 015 115 <0.10 % ±12 Vdc 20 MOhm

0/40 mV 016 116 <0.10 % ±12 Vdc 20 MOhm

0/50 mV 017 117 <0.07 % ±12 Vdc 20 MOhm

0/60 mV 018 118 <0.07 % ±12 Vdc 20 MOhm

0/70 mV 019 119 <0.07 % ±12 Vdc 20 MOhm

0/80 mV 020 120 <0.07 % ±12 Vdc 20 MOhm

±5 mV 021 121 <0.15 % ±12 Vdc 20 MOhm

±10 mV 022 122 <0.10 % ±12 Vdc 20 MOhm

±20 mV 023 123 <0.10 % ±12 Vdc 20 MOhm

±30 mV 024 124 <0.10 % ±12 Vdc 20 MOhm

±40 mV 025 125 <0.10 % ±12 Vdc 20 MOhm

±50 mV 026 126 <0.07 % ±12 Vdc 20 MOhm

±60 mV 027 127 <0.07 % ±12 Vdc 20 MOhm

±70 mV 028 128 <0.07 % ±12 Vdc 20 MOhm

±80 mV

029 129 <0.07 % ±12 Vdc 20 MOhm

Load cell

CORRECTED MILLIVOLT SIGNAL

Throughout this document, the ‘Input signal low’ (In.Lo), ‘Input signal high’ (In.hI) and ‘Tare’ (tArE) parameters and the ‘Input signal value’

(InP.S), are expressed in ‘corrected millivolt’ units, and are indicated with a ( ’ ) symbol. The millivolt values of these parameters may not be the same

as the millivolt values directly measured at the input signal terminals. The parameter values are corrected to a theoretical excitation voltage scale

of ‘5 Vdc’. The instrument reads the real value of the excitation voltage at the load cell, and compensates for any variations away from the ‘5 Vdc’

theoretical value.

For troubleshooting purposes, the ‘Measure’ function displays the real millivolt signal at terminals (see section 13.5). This value can be compared

with the value provided by a handheld millivolt meter connected at the input terminals.

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