DayTronic 3770 User manual

MODEL
3770
DC STRAIN GAGE CONDITIONER
SB.1.1
INSTRUCTION MANUAL
3700
Instrument Series

Model 3770 DC STRAIN GAGE PANEL METER
3770
1.A.0.3770
1 G ENERAL D ESCRIPTION AND S PECIFICATIONS
The Model 3770 is a single-channel panel instrument for traditional wheat-stone bridge type
sensors; intended for applications involving conventional full arm bridges from 120 to 10K Ohm
transducers with mV/V ratings between 0.5 and 10.0 mV/V full scale. The 3770 will supply
excitation, conditioning and provide a calibrated Engineering Unit's display and analog output
signals for the measurement of force, load, torque, pressure and other parameters associated with
DC based full bridge sensors. The 3770 is front panel configurable with user selectable wide
gain, zero, symmetry, and selectable analog output of voltage and current signals. Display is user
configured and can be independently adjustable for engineering unit scaling up to ± 199950
independent of the analog full scale signal.
The Model 3770 can be either calibrated by the “two-point (dead-weight)” process involving
known input parameters or through the “Shunt” method using front panel push buttons or rear
connections for simulated calibration using a known resistance provided internally by the 3770
or through a user installed resistor value.
FRONT PANEL VIEW OF 3770 CONTROLS (Front Display Cover Removed)
1 2 3 4 5 6 7 CF
CCFF
1 . X . X . X . X 0
FINE ADJUST
ZERO SPAN 1.X.X.X.X 0
ZERO SPAN
WIDE ADJUST
5000
10000
20000
SYM
DISPLAY SPAN
TARE
+ CAL - CAL
1 2 3 4 5 6 7
ANALOG CTRL
FINE ADJUST
COARSE ZERO
FINE ZERO
COARSE SPAN
FINE SPAN
WIDE ADJUST
ZERO
SPAN
DISPLAY CONFIGURATION
Sw 1,2,3,4 DECIMAL POINT PLACEMENT
Sw 5 DUMMY ZERO
Sw 6 & 7 DISPLAY RESOLUTION
+ CAL
Shunt Positive
- CAL
Shunt Negative
TARE
ANALOG CONTROL SETTINGS
1 – VOLTAGE OUTPUT – 5.0 or 10.0 VDC
2 - CURRENT OUTPUT – 4-20 mA
3 - ANALOG FILTER – 20 / 200 Hz
4 - ANALOG FILTER – 20 / 2 Hz
5 - SHUNT – INTERNAL or EXTERNAL
6 - EXCITATION VOLTAGE - 10 or 5 VDC
7 - Not Used
DISPLAY SPAN
COARSE
FINE
SYMMETRY
OFF
Page 1

Model 3770 DC STRAIN GAGE PANEL METER
3770 SPECIFICATIONS
Measurement Range: Adjustable; 0.5 to 10 mV/V; nominal full-scale. Dependent on Excitation level selected
Transducer Types: Conventional 4-arm strain gage bridges, 120 to 10 k ohm
Excitation: Selectable: 5.0 or 10.0 Vdc, with remote sense lines. Up to 70 mA.
Physical Parameters: 5.68” W x 2.84” H x 7.06” D; weight 3.25 Lbs.
Analog Output: selectable; ± 5, ± 10 Vdc, 4-20mA or 4-12-20mA (20% over-range on voltage outputs only)
Operating Temperature: 0 to +55 Degrees C, 5 to 95% relative humidity, non-condensing
Amplifier
Normal - Mode Range: ± 0.2 V RMS operating; ± 28 V without instrument damage
Common - Mode Range: ± 3 V
Input Impedance: Differential >10 MΩ
Offset:vs. Temperature: ±30 ppm µV/°C; vs. Time: ±10 ppm/month
Gain Accuracy: Limited only bycalibration accuracy
Gain Stability: vs. Temperature: ±30 ppm/°C; vs. Time: ±10ppm/month
Linearity:better than ± 0.03% offull scale
Filter: 3-pole modified Butterworth; 3 dB down at 2 Hz, 20 Hz or 200 Hz; selectable. Fast output
always enabled, 5 KHz response (J3 Pin 3).
Step-Response Settling Times for the 3770 (in milliseconds)
3db Frequency To within 1% within .1% within .02%
Fast Output 5000 Hz 0.14 0.10 0.08
Selectable Output 200 Hz 3.7 5.0 5.6
20 Hz 37 50 56
2 Hz 370 500 560
1. a P ANEL M OUNTING
You can easily mount the instrument in your own precut panel. Cutout dimensions for
a panel-mounted unit are standard
DIN ; panel thickness should not exceed 6 mm (0.24
in).Simply unscrew the two rear-panel CLAMP SCREWS and slide the CLAMP
SLIDES rearwards out of their grooves (THE FRONT BEZEL NEED NOT BE
REMOVED). Insert the unit through the panel cutout, from the front of the panel (if
the unit has rubber feet, these will have to be removed). Then reinstall the
CLAMP SLIDES, and tighten the CLAMP SCREWS until the instrument is securely
mounted.
Page 2
Power: 85 - 264 VAC @ 0.2 amps; 47 - 63 Hz

Model 3770 DC STRAIN GAGE PANEL METER
2 C ONNECTIONS
The Model 3770 I/O CONNECTIONS are via removable screw terminals which will accept wire sizes from
AWG 12 to 26. NOTE:The recommended transducer cabling would be eight wire, twisted pair, individually
shielded - wired as indicated (Fig. 6) Sense lines must be connected at the transducer (as recommended) or
at the 3770 screw terminals - as a minimum. Table 1 denotes screw terminal assignments
Rear Panel Connections
R CAL +
SHUNT
HOLD
TARE
TARE ENABLE
EXCITATION EXCITATION
SENSE
SENSE
SIGNAL
SIGNAL
CAL SENSE
SHIELD
VDC COM
V OUT SEL
V OUT FAST
4-20 mA COM
4-20 mA OUT
+
_ _
_
+ +
SHUNT
N/C N/C
LOGIC COM
R CAL -
Table 1
Connector Screw Terminal
Number Terminal Label Function
J1 1 N/C No connection
J1 2 N/C No connection
J1 3 HOLD Input Analog Hold command
J1 4 TARE Input Analog TARE command
J1 5 TARE ENABLE External TARE enable input
J1 6 LOGIC COM Logic Common
J1 7 R CAL + Remote Positive SHUNT Command
J1 8 R CAL - Remote Negative SHUNT Command
J1 9 SHUNT External Shunt Resistor Connection
J1 10 SHUNT External Shunt Resistor Connection
J2 1 + EXCITATION + Excitation Power
J2 2 - EXCITATION - Excitation Power
J2 3 + SENSE + Sense excitation control
J2 4 - SENSE - Sense excitation control
J2 5 + SIGNAL + Signal Input from sensor
J2 6 - SIGNAL - Signal Input from sensor
J2 7 CAL SENSE Calibration Sense for Shunt
J2 8 SHIELD Case Shield for cable termination
J3 1 VDC COM - Signal Output Voltage Common
J3 2 V OUT SEL + Signal Output Voltage – Filter Select
J3 3 V OUT FAST + Signal Output Voltage – 5 kHz Filter
J3 4 4-20 mA COM Current Output Common
J3 5 4-20 mA OUT Current Output Signal
Page 3

2 C ONNECTIONS
J1 – Shunt Resistor Connections. Two terminal pins are provided via the J1 rear connector
for installation of an external shunt resistor. Terminal connections are used to install a user
defined resistor as determined by the sensor’s calibration data sheet or pre-determined by
the user. When an externally installed resistor is used, the ANALOG CONTROL switch 5 is
required to be in the External position (Switch 5 DOWN).
Note: The 3770unit comes with an internally installed 59K Ohm resistor, asstandard, and
enabled when the front panel ANALOG CONTROL Switch# 5 is in the Internal position
(Switch 5UP).
Note: When a sensor has an integrated shunt resistor, the ANALOG CONTROL switch
setting needs to be in the External position and a shorting wire in place of the external
shunt resistor position. This provides the electrical path for the Calibration Sense line to
enable the sensor’s internal shunt resistor when the + or – Shunt Calibration rear terminals
or push buttons are activated.
SHUNT Resistor – User Provided
(Note: ANALOG CONTROL switch
5 must be in the External position)
External Shunt Resistor Connections
J1
SYNC
M / S ENABLE
TARE ENABLE
HOLD
TARE
LOGIC COM
R CAL +
R CAL -
SHUNT RESISTOR
SHUNT RESISTOR
NOTE: Daytronic Shun
tCalibration circuit, when activated, will place theShunt resistor across
the +Sense Line (for positive s hunt) orthe – Sense Line (for negative shunt) withthe
connection of the Sensor’s Ca libration Sense line located on the J2connector - which is
recommend tobe connected to the + Signal line. When not activated, the Calibration Sense line
is buffered as to not affec t the sensor’s operational characteristics.
Page 4
DC STRAIN GAGE PANEL METER
Model 3770

Model 3770 DC STRAIN GAGE PANEL METER
2 C ONNECTIONS
J1 – Shunt Command Connections. Connection is used to activate the positive or negative
Shunt calibration command from the rear panel. When the + or – R CAL terminal is
connected to LOGIC COM via a switch or relay, the installed Shunt resistor will be
connected across + Signal and + Sense or – Sense depending on the Shunt polarity chosen
and the CAL SENSE connection. CAL SENSE line is normally connected to + Signal for
proper signal activation.
Fig. 4
SHUNT Command
Connections
J1 - SHUNT Activation
Connections
Connecting LOG COMMON to the R CAL + or
R CAL - terminal will activate the installed
shunt resistor (internal or external) across the
connected four arm bridge sensor for
simulated calibration & verification check of
the sensor’s electrical characteristics.
LOGIC COM R CAL +
N/O
Switch
J2 - HOLD & TARE Connections. Connection is used when external control of the "HOLD"
or "TARE" features of the unit are enabled and are controlled by an external switch, PLC or
relay. The LOGIC COM signal is used to activate the analog HOLD or Analog TARE
(offset) to the meter's display and analog output signals present on J3.
Fig. 5
J1 Logic Controls
HOLD IN Activates Analog HOLD when connected to LOGIC COMMON
TARE IN Activates Analog TARE when connected to LOGIC COMMON
TARE ENABLE Enables remote TARE and disables front panel TARE when connected to LOGIC COMMON
LOGIC COMMON Connection to enable rear panel features
Push Button, Contact Relay,
Switch…..
LOGIC COM
HOLD
TARE
TARE ENABLE
Page 5

Model 3770 DC STRAIN GAGE PANEL METER
2 C ONNECTIONS
Fig. 6 - Transducer Cabling – DC Strain Gage- J2
+ SENSE
- SENSE
+ EXCITATION
- EXCITATION
+ SIGNAL
SHIELD
- SIGNAL
CAL SENSE
EXCITATION EXCITATION
SENSE
SENSE
SIGNAL
SIGNAL
CAL SENSE
+
_
_
_
++
SHIELD
Note: Sense lines must be connected at the transducer or at the instrument for proper operation.
J3 - Analog Connections Provides analog outputs from the meter's signal conditioning area in the form
of ±5Vdc or ± 10 Vdc (selectable via the front panel controls) and 4-20 mA (or selectable 4-12-20mA).
Full scale output isreferenced to the display "range" selected (5000, 10000, or20000). I.e.Ifrange
10000 isselected, the analog output will be 5 Vdc or 10 Vdc, as determined by the front panel controls
(or 20mA FS) when in the default/home position and the display reads 10000 (irrespective of the
decimal point).
12345
Analog Voltage
Output
+/- 5 Vdc or +/- 10 Vdc with
fixed cutoff filter @ 5 KHz
Analog Voltage
Output
+/- 5 Vdc or +/- 10 Vdc with
front panel selectable cutoff
filter @ 2/20/200 Hz
Analog Current
Output
4-20mA, 4-12-20mA
at selected cutoff filter
+ SIGNAL
- SIGNAL
- SIGNAL
+ SIGNAL
+ SIGNAL
- SIGNAL
J3 - Analog Output Connections
Pin 1 Voltage Common (- Signal out) reference for Pin 2 and Pin 3 + Signal Voltage Output.
Pin 2 Voltage Output Selected (+Signal out) reference to Pin 1. The Full Scale Voltage is determined by
the position of switch 1 -VDC on the Conditioner Controls. Output response is determined by the
position of switch 3-FIL and 4- FIL on the Analog Controls.
Pin 3 Voltage Output Fixed. (+ Signal out) reference to Pin 1. Full Scale Voltage is determined by the
position of switch 1-VDC of the Conditioner Controls. Filter response is fixed at the highest
analog signal response of 5 KHz.
Pin 4 4-20 mA Current Output Common (- Signal) reference for Pin 5 Current Output.
Pin 5 4-20 mA Current Output (+Signal) reference to Pin 4 Current Output Common. The Current
Output is selectable for 4 - 20 mA or 4-12-20 mA as determined by the position of switch 2 -mA
of the Conditioner Control switch(s) on the Front Panel.
Page 6

Model 3770 DC STRAIN GAGE PANEL METER
3 C ONTROLS
Display Range and Decimal Point Selection
Switch 1 - selects decimal point for position X.XXXXX
Switch 2 -
selects decimal point for position XX.XXXX
Switch 3 -
selects decimal point for position XXX.XXX
Switch 4 -
selects decimal point for position XXXX.XX
Switch 5 -
enables dummy zero display digit XXXXX 0
Switch 6 & 7 -
selects Display Full Scale Range.
Range will equate to an analog output value of ± 5 Vdc or ± 10 Vdc per Analog Control switch placement.
Selection is set for 1 count in 5000, 2 counts in 10000 and 5 counts in 20000.
Analog Zero and Span Adjustments
Coarse Zero - 22 Turn potentiometer adjustment for balance control of analog offset signal
Fine Zero - 25 Turn potentiometer for fine balance control of analog offset signal
Coarse Span - 22 Turn potentiometer adjustment for analog control of gain
Fine Span - 25 Turn potentiometer adjustment for analog control of fine gain
Page 7

Model 3770 DC STRAIN GAGE PANEL METER
3 C ONTROLS
Analog Wide Gain and Zero Controls
Two - 16 Position switches are used for wide control adjustment of the analog output signal from the
3770 meter; this in turn affects the digital readout for engineering unit’s adjustments as determined by
the display settings.
Wide Zero - 16 position switch to adjust wide zero-balance authority, approx. 13% /position
Wide Span -
16 position switch to adjust wide range gain for 0.5 to 10 mV/V sensors
Display Span Adjustments
Used to adjust the digital readout of the 3770 meter, the user calibrates the analog output for a specific
span value and then adjusts the readout for proper engineering units display. “OFF” position indicator
defines the default position. i.e. 5.000 Vdc for the analog outputs equals to 5000 counts on the display.
Display Coarse Span - 16 position switch to adjust wide span / gain authority for the display
Display Fine Span -
25 Turn potentiometer for fine span / gain control of display reading
Display “OFF” – switch position “F” which disables the Adjustable Span feature of the display
Page 8

Model 3770 DC STRAIN GAGE PANEL METER
3 Controls
Analog Control Settings
Front panel controls configure the Signal conditioner section for excitation level, mode of the analog output
signal, low pass filter characteristics and shunt calibration being internal or external.
1 – 5 Vdc Output - UP sets the analog output FS to 5 Vdc, DOWN is 10 Vdc
2 – 4 - 20 mA - UP sets the analog current output for 4-20 mA , DOWN is 4-12-20ma
3 – 20/200 Hz - UP selects 20 Hz filter. DOWN selects 200 Hz filter
4 – 20/2 Hz - UP selects 20 Hz filter. DOWN selects 2 Hz filter
5 – SHUNT Internal / External - UP selects the Internal Shunt Resistor – 59K, DOWN is External
6 – Excitation - UP selects 10 Vdc excitation to the sensor, DOWN selects 5 Vdc
7 – Not Used
With all switches in the UP position, the unit will have the following settings:
•10 Vdc Excitation voltage
•The full scale analog output will be 5.000 Vdc
•The current output will be set for 4 ma = zero and 20 ma will = positive full scale
•The analog low pass filter will be set for 20 Hz
•Shunt calibration resistor will be set for the internal 59K Ohm resistor value
Note: The Excitation (switch 6) placement is used to select the mV/V input range of the unit. 5 Vdc setting
will accept sensors from 5.0 to 10 mV/V. 10 Vdc setting will accept .5 to 5.0 mV/V sensors.
Analog Control Settings for Conditioner Configuration
1 - VDC OUT
2 - mA OUT
3 - FILTER
4 - FILTER
5 - SHUNT
6 - EXC
7 - N/A
5
4-20
20 Hz
20 Hz
INT
10
10
4-12-20
200 Hz
2 Hz
EXT
5
Down
Function
Analog Control Settings (red switch array)
The selection of the 7 front panel analog control
settings will configure the signal conditioning
section of the meter. The position of the switches
will depend on the type of sensor, its parameters
and the expected analog output signal levels
along with the output signal’s 3db roll-off
response characteristics.
Page 9

Model 3770 DC STRAIN GAGE PANEL METER
3 Controls
Analog Symmetry, + CAL, - CAL, TARE
SYM Symmetry - Adjust the negative gain slope for symmetrical analog adjustment and display
reading with reference to the positive span value. 20 Turn potentiometer, with approx. ± 2%
full scale authority
+CAL Positive Calibration – Activates the SHUNT Positive by switching in the external or internal
shunt calibration resistor across the Cal Sense and + Sense leads of the bridge.
-CAL Negative Calibration – Activates the SHUNT Negative by switching in the external or
internal shunt calibration resistor across the Cal Sense and - Sense leads of the bridge.
TARE TARE - Push / Push switch. When enabled, offsets the present sensor signal input to "Zero".
When activated, a green LED light will illuminate. During activation process, LED will light
Yellow. If disabled, or out of range, LED will be RED. TARE maybe remotely activated via
rear J1 connections. Front panel TARE can be disabled via J1 Pin 5connected to Logic
Common, Pin 6. Maximum TARE capability is approx. 60% of full scale reading.
Page 10

Model 3770 DC STRAIN GAGE PANEL METER
4. CALIBRATION
This section contains the instructions for calibrating the 3770. Included is a functional description of the instrument
front-panel (see Page 1). To perform calibration, proceed as follows.
(a) Connect Sensor and Analog terminals as required. Connect and apply power to the unit. The front-
panel digital display should light indicating the application of the AC input power. Allow 10
minutes of warm up for stabilization of transducer characteristics. Remove the front cover of the
3770 unit by removing the two small Phillips screws on the front panel. TARE should not be
activated.
(b) Center the Zero and Fine Span potentiometers by rotating the potentiometers CW until you feel the
“end stop” or by the number of turns accomplished (Coarse is 22 turn, Fine is 25 turn). Rotate the
potentiometer back to the middle of their range (Coarse 11 turns, Fine 12-13 turns). This will
establish the adjustments middle authority.
(c) Position the front panel switches to the desired settings for the application. Refer to Section 3 for
details.
(d) Relax the sensor input to “zero” load and adjust the Wide Zero and Fine Zero controls until the
meter reading is achieved at the point which will be the “zero” value reference.
(e) Once the Zero position has been established, apply a known load typically in the nominal working
range of the sensor. With the load active and stabilized, adjust the Wide Span, Coarse Span and
Fine Span controls until the display reading required is achieved.
(f) Return the sensor to the "Zero" position and re-adjust the Coarse Zero and Fine Zero controls for
the desired reading or analog output of the unit. Repeat the Span (step e) adjustment as necessary to
achieve the proper reading or analog output. Note that changes in Span (Gain) will affect Zero.
Span and Zero re-adjustments may need to be repeated to obtain the desired reading. (Note that the
3770 meter also has independent display adjustment capability to where the digital display can be
adjusted independently to the analog output signal of the unit so as to achieve proper analog output
levels from the meter.)
(g) Once the Zero and the Gain (SPAN) adjustments have been accomplished, if needed - the user can
adjust for Negative non-symmetrical value (as referenced by the positive SPAN value) by utilizing
the front panel Symmetry control when the load is Negative. To accomplish this, apply a known
negative load and adjust the symmetry control for the correct readout or analog output signal
required. Note the Symmetry control has approx. ± 2 % full scale authority.
(h) Once completed, replace the front display lens cover to the original position and ensure proper shielding and
grounding have been done to the meter. Minor calibration adjustment may be accomplished using the front
panel potentiometer for zero and span.
Display Calibration
The 3770 instrument display has separate adjustment controls that are independent of the
analog output controls - allowing the user to alter the display reading to a value that is suited for the display while
maximizing the analog output amplitude. In the standard – default switch position (as marked near the Coarse
Display Span control), the display has a fixed full scale reading set by the display range switches of 5000, 10000 or
20000 counts. At theses settings the full scale analog output signal will be 5 Vdc or 10 Vdc, as selected via the
analog controls. To accomplish the display adjustment change, the user would first set the desired display range
and decimal location using the display dip switches, adjust the analog output to the desired level and then adjust the
display Coarse then Fine span controls for the required digital readout.
Page 11

Model 3770 DC STRAIN GAGE PANEL METER
4. CALIBRATION – Shunt Calibration
This section contains the instructions for calibrating the 3770 using the Shunt calibration method.
(a) Connect Power, Sensor and Analog terminals as required. Apply power. The front-panel digital
display should light indicating the application of the AC input power. Allow 10 minutes of warm
up for stabilization of transducer characteristics. Remove the front panel cover of the 3770 unit
which is held in place by the two small Phillip head screws.
Note: The 3770 unit has an internal 59K Shunt resistor installed within the unit. If a different
resistor value is to be used to correspond to the transducer’s calibration sheet; install the resistor
on the rear J1 terminals provided and place the Analog Control Switch 5 to External. Shunt
calibration will only activate if the CAL Sense line is connected to the + or – Signal lines on the
transducer input connector J2.
For transducers with an internally installed shunt resistor: 1.) Cal Sense should be attached to the
transducer’s shunt activation connector pin; 2.) External Shunt selected on the Analog Controls;
3.) A shorting wire is to be installed in place of the External Shunt resistor terminals on the rear
of the unit.
(b) Center the Zero and Span potentiometers as needed by rotating the potentiometers fully CW
(Coarse is 22 turns, Fine is 25 turns), then reverse direction - CCW (Coarse 11 turns and Fine 13
turns) to obtain mid-authority of the controls. Typically this is done on initial calibration. When
recalibrating for minor adjustments this may not be required.
(c) With mechanical Zero or Balance established at the transducer (transducer “relaxed”); Adjust
Wide Zero then Coarse Zero and then Fine Zero for the Zero position reading on the display or
the desired analog output signal. Display can be adjusted independently to the analog signal.
(d) Depress and hold the + CAL button while adjusting the Wide Span, Coarse Span and Fine Span
controls, as needed, for precise engineering units reading on the display as determined by the
sensor’s calibration sheet or other reference data (see Equivalent Input shunt calculation below).
(e) Repeat Steps (d) and (e) to obtain proper measurement readings since the Gain – Span controls
will affect the Zero amplification of the input signal.
(f) Once completed, if the sensor is going to be utilized in the Negative or CCW mode, depress and
hold the – CAL button and adjust the Symmetry control for a proper symmetrical reading of the
shunt input as noted on the sensor’s calibration data sheet. Note the Symmetry control affects the
Negative Span for approx. ± 2% of full scale adjustment control.
(g) Release the Cal button and adjust Zero as needed. Re-install the front panel to the instrument.
Minor adjustments and controls are assessable via the front of the unit.
Page 12

Model 3770 DC STRAIN GAGE PANEL METER
4. CALIBRATION (cont.) – Shunt Calibration Equivalent Calculation
If dead weight calibration is not practical and the transducer calibration data is unknown, the
Equivalent Input value for the factory-installed calibration resistor can be approximated as follows,
assuming that the mv/v sensitivity rating of the transducer and the bridge resistance is known.
X = 25000 x Rb
K x Rc
Where X = Equivalent Input, % of full scale
Rb = bridge resistance, ohms
K = transducer sensitivity, mv/v full scale
Rc = calibration resistance, ohms (59 K installed)
Sample Calculation: Assume that K = 3.000 mv/v for a 5000-pound load cell (full scale) with a bridge
resistance of 350 ohms and using the internal 59K Ohm shunt resistor.
25000 x 350
59000 x 3 = 49.44% of full scale = 2472 pounds
When + CAL is depressed, input sensor is at zero, display is on the 5000 range, adjust the readout for 2472
Display Calibration The 3770 instrument display has separate adjustment controls that are independent of the
analog controls which allow the user to alter thedisplay reading to a value that is suited for theengineering units display
reading required. The additional span controls allow the user theflexibility to adjust the display reading as referenced tothe
analog signal orreferenced tothe defaulted front panel display dip switches. Ina standard – default “OFF” switch position
ofthe Coarse Span control, the display has a full scale reading set bythe display range switches of 5000, 10000 or 20000
counts. Atthe selected reading the full scale analog output signal will be 5 VDC or 10 VDC, asselected by the Analog
Controls of the unit. Toaccomplish the display adjustment change, theuser would first set the desired display range and
decimal location using thedisplay dip switches, adjust - calibrate the analog output to thedesired amplitude level and then
adjust the display Coarse and Fine span controls for therequired digital readout.
Page 13
Tech Tip: The inability tobalance correctly where the unit output reads totally off scale andthe zero controls have no
authority canvery likely be the result ofa damaged or defective transducer orcable. This possibility can beconfirmed (or
eliminated) by substituting a transducer and cable known to bein good condition or bysimulating a balanced transducer, using
either a commercially available transducer simulator orthe simple star bridge arrangement shown below. The star bridge
simulates a conventional four-armbridge in an exact condition ofbalance. Toconstruct a star bridge connect four resistors as
shown; use180-ohm resistors to approximate a 350-ohm bridge.
Neither the resistor values nor temperature
characteristics are critical. Solder two
excitation resistors together, and then solder
the two Signal resistors together. Next, connect
the two junctions together using a separate
wire as shown. There is a good reason for this
method of construction, and it should be
followed. Connect the substitute or simulated
transducer to the module I/O connector using
a short 4-wire cable configuration as shown in
Figure 4. Attempt to balance the substitute or
simulated transducer. If conditions now appear
to be normal, the transducer or cable is at fault.
If the previous difficulties persist, the meter is
at fault.

Model 3770 DC STRAIN GAGE PANEL METER
Tech Tip on use of wide range settings for the DC Strain Gage Conditioner
Due to multiple amplifier stages within the 3770 instrument, attention to the proper gain setting and understanding of
the sensor inputs should be reviewed to produce a linear- amplified analog output signal and display reading.
The wide span – gain control (as shown in the front panel diagram) has 16 positions to amplify the incoming signal by
incremental steps. Each step is positioned so the Coarse and Fine Span potentiometer controls overlap each step to
provide a continuous linear gain of the signal from 0.5 mV/V to 10.00 mV/V full scale. Below is a table of each wide
gain steps, indicating the nominal low and high input signal range per position – full scale in mV/V to the meter.
Note: When using 5 V excitation, increase the table values by a factor of 2.
Wide Span
Position
SPAN-Low
mV / V
SPAN-High
mV / V
0
3.90
5.80
1
3.30
4.90
2
2.90
4.20
3
2.50
3.60
4
2.10
3.10
5
1.80
2.70
6
1.50
2.30
7
1.30
1.90
8
1.10
1.70
9
1.00
1.40
A
0.84
1.20
B
0.72
1.00
C
0.62
0.92
D
0.53
0.80
E
0.45
0.65
F
0.38
0.58
DC Strain Gage Sensors sensor:
DC Strain Gage Sensors will typically specify their electrical sensitivity in mV/V for traditional foil gage transducers
or in mV full scale for semiconductor type sensors; either type will function with the 3770 unit as dictated by the
excitation voltage needed along with the full scale output of the sensor. The 3770 has selectable excitation of 5 and
10 Vdc and a maximum specified input of 50.0 mV (with 20% over-range) into the meter. As a reference, the above
table can be used as a guide to determine the working full scale range of the transducer during calibration and the
proper position of the Wide Span control. Note that additional gain or less gain can be accomplished as needed if an
expanded or reduced area of the sensor measurement level is required.
Page 14

Model 3770 DC STRAIN GAGE PANEL METER
DC Strain gage Panel Meter 3770
Product Warranty and Repair
Daytronic Corporation warrants its products to be free from defects in mate
rial
and
workmanship, under normal and proper use in accordance with our
instructions,
for the period of time specified below. Our liability under such
warranty or in
connection with any other claim relating to the products shall
be limited to, at our
option, the repair or replacement of any products or parts
or components thereof
which are returned to us freight prepaid and which are
defective in material or
workmanship or the refund of the purchase price to
the Buyer.
ANY PRODUCT FOUND TO BE DAMAGED THROUGH CUSTOMER
NEGLIGENCE OR MISUSE MAY BE EXCLUDED FROM ANY AND ALL POLICIES
CONTAINED IN THIS DOCUMENT.
ALL EQUIPMENT TO BE REPAIRED OR REPLACED UNDER WARRANTY MUST BE
RETURNED TO THE FACTORY.
Before returning a product or products for any reason,
the customer must call
Daytronic Customer Support Services at [phone] to
request a
RETURN MATERIAL AUTHORIZATION (RMA). Once the customer has provided
the necessary information and has been assigned a specific RMA, the product(s) in
question may be returned to Daytronic by shipping it
Daytronic Corp., 1000 New Durham Road, Edison, New Jersey 08818
Daytronic Customer Service: 1-800-668-4745 [e-mail]
Daytronic Corporation Dayton OH USA
www.Daytronic.com
Doc # 92363.00