Fema I4 Series, Руководство пользователя

Страница: 8 / 24

F E MA · MANUFACTURING FOR INDUSTRIAL AUTOMATION 8
10. Input signals
10.1 Load cell signals
Table 12 | Connection example for load cell signals
1 2 3
Vexc -
mV -
sense -
4 5 6
Vexc +
mV +
sense +
MEASURING LOAD CELL SIGNALS
The instrument can be configured to measure load cell
signals, with pre-configured 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 configured.
‘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 predefined input-output configuration 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 specifications. Do not
connect active signals to the excitation voltage terminals.
OUTPUT SIGNAL
The output signal is configurable 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.