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E725/AC LVDT Signal Conditioning Indicator/Conditioner Unit

E725/AC image

With Free Microsoft Excel Data Logger Application download.

The RDP Electronics E725/AC LVDT signal conditioning unit is an indicator/conditioner for use with most LVDT and inductive displacement sensors. Our E725/AC LVDT signal conditioning amplifier units provide the excitation for the transducer as well as conditioning the return signal. It also incorporates a digital display. Our digital indicator unit is microprocessor based and has an auto-zero function to zero the transducer display on command.

Where the transducers are identical, two may be connected to one digital indicator using the optional second LVDT amplifier input card. The digital indicator may then be set to display either of the input channels as well as sum and difference.

Unlike many signal conditioning units of its type, the E725 has a high bandwidth analogue output of 250Hz. Both voltage and 4-20mA outputs are available. At the heart of our panel meter is a microprocessor. This provides some useful features such as peak and trough store, remote/auto zero, push button configuration, signal hold, calculated channels and of course digital re-transmission. The unit however remains as simple to use as a panel meter.

The E725 supports RS232 as standard and, RS485 as an option. The RS485 is addressable so that up to 256 units can be connected together to form a communications network. Four TTL limits with front panel LEDs are standard, with voltage free relays offered as an option.


E725 rear panel
Dimensions (1/8 DIN) Dimension Wide High Deep
Bezel size 96mm 48mm Max depth 180mm (incl connectors)
Panel cut out 93mm 45mm
Power Supply Standard Options
Power Supply Additional Charge Options
Power Supply Tolerance: -
Power Drawn (nominal at stated voltage)		 230ac or 115Vac
105Vac, 5Vdc, 12Vdc or 24Vdc
Ac versions (+5% / -15%). Dc versions (+50% / -25%)
Ac versions 7VA, Dc versions 7W.
Display Detail 5 digit 13.2mm red LED
Display Resolution 1 in ±99999
Display Update 3 Hz
Display Auto-Zero Range 100% display range
A-D converter resolution. Significantly better than 1 in ±99999
Transducer Excitation 1.1V sinusoidal rms at 5kHz, 30mA max.
LVDT Amplifier Bandwidth Flat to 250Hz
LVDT Amplifier Input Impedance 100k Ohms differential
Amplifier Linearity (typical) ±0.05% F.S.
Amplifier Noise Output 5mV (or 20µA) pk to pk typical
Amplifier Output. Standard - Transducer -FS to +FS = 0 to 10V or 4 to 20mA
On request - Transducer 0 to +FS = 0 to10V or 4-20mA
Amplifier Signal input range 33mV to 4V rms. (All RDP LVDTs)
Amplifier Zero Adjustment Range analogue output only) ±1.5V (analogue output)
Limits (Standard) Quad limits with front panel annunciators and optional voltage free relays. 20ms operation time (max)
Limits (Optional fast version) 2 limits (mechanical or solid state to order), 5ms operation time. Replaces standard limits.
Max/Min (Min pulse width for 1 digit accuracy) NOMINALLY 40ms (filter value 1), 500ms (filter value 5)
Max/Min (Optional fast version), accuracy for 0 to FS step Change in 10ms=0.1% F.S.
Change in 1ms=0.2% F.S.
Second transducer input Transducers sensitivities must be within 15% of each other. They must have a common full scale value.
External Digital Control ZERO, RESET and HOLD
Serial Interfaces RS232 (standard), RS485 (optional)
Temperature range -10°C to 45°C (ac power)
-10°C to 55°C (dc power)
Weight Dc supply; - 430gms max
Ac supply: - 510gms max.
Input and Output connections Transducer and option connectors :- 9 pin D type.
Digital I/O:- 15 pin D type.
Analogue:- 3.5mm jack.
Environmental Protection IP50 (whole unit), IP65 max (front panel with sealant)


Order Code Structure

E725 Supply Voltage Input Card Option board Serial output Special Options
230 =230Vac AC =LVDT & inductive 0 =None 0 =RS232 0 Factory selection (use 0)
115 =115Vac R =4 mechanical relays 1 =RS485
105 =105Vac RS =4 solid state relays
5 =5Vdc FR =2 fast mechanical relays EG:-E725-230-AC-2AC-0-0 is
powered from 230Vac,
has a second input
and has an RS232 output.
12 =12Vdc FRS =2 fast solid state relays
24 =24Vdc FM =Fast max/min board
2AC =Second AC input board

Table of option card compatibility
Only one option card may be fitted. However, the inclusion of an option card may affect the operation of other features.
AC 2AC FM R/RS FR/FRS
Function keys:- 3 keys may be programmed which have a gain and zero offset from the primary channel. (allows multiple engineering units for example) *
Polynomial Linearisation (user can generate a polynomial to linearise a transducer)**
Multi-point calibration (uses 11 calibration points to help correct transducer errors)**
Software limits (4 off)
*Function keys are fixed to give A, B, (A+B)/2 and A-B, A and B being the two input channels.
**The E725 has a facility that allows a user-selectable value to be added to the display reading, it is called 'engineering offset'. This facility is not available if multi-point or polynomial calibrations are used.

Additional Information

Free data logger application. This RDP Electronics utility enables the transducer display value to be read from the 725, directly to a suitable PC having an appropriate version of Microsoft Excel. The value displayed on the panel meter can be logged in real time. The user may configure Microsoft Excel to produce real-time graphs etc. A correctly wired serial lead is required.

The E725/AC can have two LVDT inputs and can be configured to show, and output via the analogue output either channel A, channel B, A+B or (A+B)/2. The two transducers must be of the same range, display the same value at full scale and have a sensitivity within 15% of each other. Voltage or 4-20mA outputs of the selected transducer display mode are available.

Calibration options include two point (zero & FS), three point (-FS, 0 and +FS), 11 point and 10th order polynomial.

The serial output can be either RS232 or RS485, the latter can have up to 256 units on the same network providing easy interface with data loggers etc.

Calibration and set-up information for the indicator/conditioner are stored on EEPROM so there is no back up battery.

All four limits can be configured as high or low, latching or momentary and normally energised.

Limits can be set on High, Low, or deviation from a nominal value.

MAX, MIN and TIR functions enable the unit to monitor important trend information for quality analysis and run-out calculations.

Due to the RDP Electronics policy of on-going development, specifications may change without notice.
Any modification may affect the specification of our equipment.