RDP Group S7DC User manual

RDP Customer Document
Technical Manual
TRANSDUCER AMPLIFIER
TYPE S7DC
Doc. Ref CD1202AF
This manual applies to units of mod status 8 ONWARDS
Affirmed by Declaration
of Conformity
USA & Canada
All other countries
RDP Electrosense Inc.
RDP Electronics Ltd
2216 Pottstown Pike
Pottstown, PA 19465
U.S.A.
Grove Street, Heath Town,
Wolverhampton, WV10 0PY
United Kingdom
Tel [phone]
Fax [phone]
Tel: [phone]
Fax: [phone]
E-mail [email protected]
www.rdpe.com
E-mail: sale[email protected]
www.rdpe.com

2
INDEX
1INTRODUCTION.....................................................................................................3
1.1 Declaration of Conformity .......................................................................................4
2. INSTALLATION.......................................................................................................5
3. CONNECTIONS......................................................................................................6
3.1 Supply / output connections....................................................................................6
3.2 Transducer connections..........................................................................................7
3.3 Full bridge Strain Gauge Transducer......................................................................7
3.4 1/4 or 1/2 bridge transducer connections................................................................7
3.5 Potentiometric Transducers ....................................................................................7
4. CONTROLS............................................................................................................9
4.01 Output Mode Link:...................................................................................................9
4.02 Excitation.................................................................................................................9
4.03 Zero.........................................................................................................................9
4.04 Fine Gain.................................................................................................................9
4.05 Gain Range (x1 to X1250).......................................................................................9
4.06 Shunt Calibration.....................................................................................................9
4.07 Bandwidth/Noise Capacitor...................................................................................10
4.08 4-20mA Offset Solder Link SP1 ............................................................................10
4.09 Relay Voltage Solder Link SP2.............................................................................10
4.10 Maximum Voltage output vs. Supply Voltage........................................................10
4.11 Maximum 4-20mA loop resistance Vs. Supply Voltage.........................................10
5. SETTING-UP PROCEDURE, Voltage Output.......................................................11
6. SETTING-UP PROCEDURE, 4-20mA Output ......................................................11
7. SHUNT CALIBRATION FACILITY........................................................................12
8. SPECIFICATION...................................................................................................13
9. FUNCTIONAL CHECKS .......................................................................................15
10 WARRANTY AND SERVICE ................................................................................16
TABLE OF FIGURES
Fig. 1 Connections & Control Locations ..........................................................................5
Fig. 2 Signal Cable Installation for Optimum EMC...........................................................8

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1 INTRODUCTION
The S7DC is an in-line d.c. amplifier intended to provide variable excitation and signal
amplification for strain gauge type transducers. It will operate from unregulated single or
dual tracking power supplies and provide up to 10V output (or 4-20mA) with transducer
signals from 10mV to 10V. This allows operation with some high output transducers (DCT,
etc.); for example, to provide 4-20mA outputs with signal inputs up to 10V.
This unit accepts both uni-polar (eg 0 to 4mV) or bi-polar (eg ± 4mV) input signals and can
produce corresponding uni-polar or bi-polar voltage outputs (ie 0 to 10V or ±10V)
sensitivities and gains given in this document refer to both. Current outputs (4 to 20mA)
are uni-polar.
Excitation, coarse gain, fine gain and fine zero controls are provided, with the facility to
connect remotely an internal shunt calibration resistor. Connections are made via screw-
terminals which, with the controls, are all mounted inside an aluminium case, sealed to
IP65 specification.
Note that the voltage output common (0V terminal) with a single (2 wire) supply voltage, is
approximately at the mid supply voltage eg with a 24 volt supply the output common is 12
volts (see section 3.1).

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1.1 Declaration of conformity
DECLARATION OF CONFORMITY
RDP ELECTRONICS LTD.
Grove Street Heath Town
Wolverhampton West Midlands
WV10 0PY
United Kingdom
We declare that the product described in this technical manual is manufactured by
RDP Electronics Limited and performs in conformity to the following:
The Electromagnetic Compatibility Directive 2014/30/EU
RoHS Directive 2011/65/EU
EMC Regulations SI2016/1091
Restriction of Hazardous Substances Regulations SI2012/3032
R D Garbett
Director
RDP Electronics Limited

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2. INSTALLATION
2.1 For EMC compliance, only multi-core cables should be used for the signal input and
output connections.
2.2 The shields of the two cables may be connected to the SCN and common terminals
of the transducer connector and output connector but, for optimum EMC, the cable
shield should be terminated as shown in Fig.2
2.3 ESD precautions should be used when working on the instrument with the lid
removed. The user should ensure he is "grounded" by use of an grounded wrist
strap or at least touching ground before touching any component, including wires,
terminals or switches.
2.4 Segregate signal/supply/output cables. Route signal cables away from possible
sources of EMI, e.g. motor/solenoid/relay cables, etc.
2.5 The transducer body should be grounded. The transducer body being clamped or
bolted to grounded metalwork, e.g. on a machine usually achieves this. Where this
does not apply and also where there is no grounding connection via the connection
cable to the S7DC, then a separate grounding wire should be connected from the
transducer body to the S7DC SCN terminal.
2.6 Ground the case, e.g. via the mounting holes provided.
Fig. 1 Connections & Control Locations
F
C
J1
RV1
B
A
B A
SP2
CON2
SUPPLY/OUTPUT
R21
SW1
GAIN
CON1
TRANSDUDER
GND
V+
0V
V-
OUT
RCAL
EXC+
EXC-
SIG+
SIG-
SCN
CAL
Transducer
Excitation
Signal
Cable
Shield/Screen
F.GAIN
RV3
SP1
RV2
V
mA
OUTPUT
EXCIT
C2
Shunt
Calibration
Ground
Supply Positive
Output/Dual
Supply Common
Supply Negative
Output (V or I)
Remote Shunt
Calibration
ZERO

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3. CONNECTIONS
3.1 Supply / output connections
a) Voltage output, single supply.
This arrangement should only be used if (b) is not possible.
If this arrangement is used, either the supply V- or the output common 0V (or both)
must be fully floating ie only one can be grounded. Failure to do this may result in
damage to the amplifier that is not covered by warranty.
b) Voltage output, dual supply (supply must be symmetrical)
Either the supply V- or the output common 0V (or both) must be fully floating ie
only one can be grounded. Failure to do this may result in damage to the
amplifier that is not covered by warranty.
c) Current output, single supply.
Ensure that the output mode link (J1) is set to mA. See Fig. 1 for location.
Note 1 Ground is connected to the case of the amplifier.
GROUND
V+
0V
V-
OUTPUT
R CAL
V+ (+10 to +36V)
V-
±3V to ±10V
-
+
GROUND
V+
0V
V-
OUTPUT
R CAL
V+ (+5 to +18V)
(0V)
V- (-5 to -18V)
±3V to ±10V
-
+
GROUND
V+
0V
V-
OUTPUT
R CAL
V+ (10 to 36V)
V-
4 to 20 mA
+
-

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3.2 Transducer connections
Before connecting the transducer, check the excitation
voltage.
Applying an excitation voltage that is too high may
destroy the transducer
3.3 Full bridge Strain Gauge Transducer
Transducer connector details are as shown in Fig. 1 and on the S7DC circuit board.
To use the shunt calibration facility, insert a link between 'CAL' and 'SIG-'.
3.4 1/4 or 1/2 bridge transducer connections
For 1/4 bridge transducers, 3 bridge completion resistors are required. The active gauge
should be fitted on arm 'C' and the bridge completion resistors in arms D, A & B.
For 1/2 bridge systems, the active gauges should be C and D, and 2 completion resistors
are required.
The bridge completion resistors should be high stability, the same resistance as the active
gauge and may be fitted either in the transducer connector, or in the designated position on
the underside of the S7DC PCB. This requires removal of the PCB from the case.
R22 replaces bridge arm D, R23 replaces bridge arm A, R24 replaces bridge arm B
Note: Mounting these resistors in the instrument is a compromise. To reduce temperature
and long lead effects, completion resistors should preferably be mounted at the
transducer and be of close tolerance and low t.c., e.g. 0.1%, 15 ppm..
3.5 Potentiometric Transducers
Select R24 value to drop at least 1.5V.
For example, with an excitation of say
10V and a potentiometer resistance of
500 ohms and R24 value of 100 Ohms,
the voltage drop across R24 = 10V /
(500+100) X 100 = 1.7V.
This raises terminal 4 to within the
common mode voltage range of the
amplifier.
Input signal = 10-1.7 = 8.3V so use the lowest gain range for ±10V output. For lower output
voltage or 4-20mA output, use lower excitation, e.g. 5V.
R24 can be added either in the solder pins on the underside of the PCB, or more easily into
the transducer screw terminals, between 'SIG-' and 'EXC-'
EXC-
A
B
C
D
EXC+
SIG+
SIG-
EXC+
SIG+
SIG-
EXC-
R24
POTENTIOMETER

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Fig. 2 Signal Cable Installation for Optimum EMC
1
2
Insert the end of the cable, plus the plastic sleeve into the metal outer shell of the
gland. The bore of the gland is a tight fit onto the cable shield, giving the required
ground contact.
3
Fit gland cap and tighten
Cable Cores
Trim
Rubber Seal
Cable Shield Double Back
Over Plastic Sleeve
Plastic Sleeve
Cable
Gland Cap
Plastic Sleeve
Metal Gland
Nut
Wall of
Instrument Case

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4. CONTROLS
4.01 Output Mode Link:
The "OUTPUT" jumper link is set to "V" for voltage output or "mA" for current output.
Three 20-turn screwdriver-adjusted controls are provided for controlling:
4.02 Excitation
- allowing continuous variation of excitation between 3V and 10V. Note: if supply is
<13V, the max. excitation voltage available is Vs - 3V. Note: for units of MOD18
onward, if operating temperature exceeds 70°C then the maximum current is 60mA,
4.03 Zero
- allowing a fine adjustment of output zero of approximately ±2V (or 0-10mA)
depending on Fine Gain setting.
4.04 Fine Gain
- allowing a 4:1 variation in amplifier gain, used in conjunction with 4.05.
4.05 Gain Range (x1 to X1250)
-sliders 1 to 4 of the 6-slider DIL switch, when used with the fine gain control,
provide an output of 5V or 4-20mA with an input signal range of approx. 4mV to
5V as shown below:
(also output ± 5V for input ±4 mV to ±5V)
SLIDERS
ON
For Mod.8 (and above)
For ±10V
OUTPUT
INPUT SIGNAL RANGE for: 5V or 4-20mA OUTPUT
4 + 3 + 2
4 –16mV
±8 to ±32mV
4 + 3
5 –20mV
±10 to ±40mV
4 + 2
18 –70mV
±35 to ±140mV
4 + 1
65 –270mV
±130 to ±500mV
4
0.25 –1V
±0.5 to ±2V
1
0.34 –1.35V
±0.7 to ±2.7V
None
1.25 –5V
±2.5 to ±10V
Note: for the two lowest gain ranges (with slider 4 off), the excitation voltage must be 5V
to provide signals within the required common mode voltage range of the amplifier.
Note: for ±10V output, the supply must be at least 22V or ±11V (see 4.10).
4.06 Shunt Calibration
- slider 5 ("C") of the 6-slider DIL switch, when set to ON connects an internal 59kΩ
0.1% resistor across one arm of the bridge.
Remote Cal. - an internal relay may be used to remotely connect the 59kΩresistor. To
operate this relay, connect the R-Cal. terminal to V- (CON 2) at any convenient point (lead
length is irrelevant) via a switch, etc.
Note 1: For normal relay operation, the supply voltage must be at least 15V. For lower
supply voltages, solder link SP2 must be made (see Fig.1).
Note 2: For normal shunt calibration, connect the CAL terminal to Sig- (CON 1). This links
the internal calibration resistor (terminal 6) to the relevant bridge node.

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If long cables are used, then cable voltage drop may cause significant shunt calibration
errors. In this case, do not link 4 to 6 but connect terminal 6 via a separate wire to the
relevant bridge node as near as possible to the transducer.
Calibration Resistor. The 59kΩ resistor (R21) is mounted on pins for ease of changing.
4.07 Bandwidth/Noise Capacitor
- slider 6 ("F") of the 6-slider DIL switch, when set to ON, connects capacitor C2 to
reduce output noise (and bandwidth). C2 is mounted on pins for convenience. Its
location is shown in Fig.1. The value is normally 47nF for standard bandwidth (BW)
and noise specifications. BW is roughly inversely proportional, e.g. to halve BW
(and noise) change C2 to 100nF.
4.08 4-20mA Offset Solder Link SP1
Normally, with SP1 not fitted, the relationship between input signal, voltage output
and current output is: zero to full scale input signal 0 to 5V or 4-20mA output.
For low supply voltage applications (<14V) or bipolar operation, e.g. for
compressive/tensile load applications, SP1 may be fitted which changes the
relationship to: ± full scale input signal = ±2.5V or 4-20mA output.
i.e. SP1 provides a ½ F.S. offset for the current output and increases the voltage
head room in the amplifier.
4.09 Relay Voltage Solder Link SP2
(Refer also to Section 4.06)
Solder link SP2 changes the supply voltage required for local or remote operation of
the shunt calibration relay as detailed in the specification, Section 8.
Units are normally supplied with SP2 not linked.
4.10 Maximum Voltage output vs. Supply Voltage.
As well as having absolute maximum and minimum values as defined in the
specification, the maximum output voltage is supply dependent and relates as
follows: -
Max output = (Total supply Voltage - 2) / 2,
E.g. for an 18V (or 9V dual rail) supply, = (18-2) / 2 = ±8V maximum output.
4.11 Maximum 4-20mA loop resistance Vs. Supply Voltage.
The maximum permissible 4-20mA loop resistance depends upon the supply
voltage to the S7DC unit. Please note, and do not exceed the maximum supply
voltage detailed in the specification.
Max loop resistance = ((Total supply Voltage - 12) x 25 ) + 100
E.g., at 10V supply, = ((10 - 12) x 25) + 100 = 50 Ohms