N2300

The N2300 is a modular system for measuring mechanical quantities, made by IEMI in Bucharest and designed at the ICE research institute in Bucharest [1]. It was exported to East Germany in 1977–1989 [1]. Its modules included carrier-frequency amplifier-conditioners (N 2313, N 2314), power supply and display modules (N 2321–N 2323), a printer (N 2324), connection, manual balancing and switching units (N 2351, N 2352), an analogue processing unit for mean, peak and RMS values (N 2334), a precision calibration unit for 1–5 kHz carrier-frequency measuring chains (N 2336) and a series of cases, racks and drawers (N 2371–N 2375) [1]. Assemblies often delivered to East Germany and at home included a one-channel analogue strain gauge, analogue and digital installations for one or 12 measuring points, and digital versions with a printer [1].

ICE’s laboratory for electronic instruments for measuring non-electrical quantities designed approved prototypes for many branches of the economy: strain gauge equipment (some configurations were exported to East Germany in 1971–1974 and 1977–1989), vibration meters, dimensional gauges, ultrasonic non-destructive testers, geophysical well-logging equipment and railway equipment [1]. Its designs were made in series at IEMI (27 types) and at the Precision Mechanics Enterprise (5 types), or in ICE’s microproduction workshop (45 types) for small series and one-off models [1].

In IEMI’s own numbering its modules were the N 23/14 strain gauge amplifier (5 kHz carrier), the N 23/21, N 23/22 and N 23/23 power supply and display modules (analogue and digital), the N 23/24 printer (N 23/24 S with an IEC 625 interface), the N 23/32 filter module, the N 23/34 peak, mean and RMS module with data storage, the N 23/38 calibration module, the N 23/51 connection and balancing module and the N 23/62 switching unit for 12 measuring points; up to 20 configurations could be built [2]. The production table lists 15 configurations made from 1979 to 1985, the most common being the one-channel analogue (437 made), one-channel digital (338), two-channel analogue (329) and six-channel (304) strain gauges [2].

In IEMI’s price list (1982–1984) its configurations cost from 22,000 lei for a one-channel analogue strain gauge to 100,000 lei for the five- and six-channel analogue versions [3]. At IEMI’s 20th-anniversary symposium in 1988 it was presented as a new generation of strain gauge equipment [4].

Modules

Annex III.2.12 describes the system: a strain gauge measuring chain consisted of a transducer (resistive, inductive, semiconductor, piezoelectric, thermoelectric and so on) and the strain gauge instrument proper, built from functional modules of standard 19-inch width assembled in standard cases to suit each measurement; all its configurations worked with a 5 kHz carrier. The prospectuses give these modules [5]:

• N 2314 – carrier-frequency amplifier (5 kHz) for static and dynamic measurements of strain, force, torque, pressure or displacement, with resistive (50–1000 Ω) or inductive (5–25 mH) transducers in bridges of 1, 2 or 4 arms: 0 … ±100,000 µm/m in 10 ranges, bridge voltage 1–8 V rms, automatic capacitive balancing, linearity 0.02%, bandwidth 1000 Hz; 177 × 55 × 400 mm, about 2 kg [5]
• N 2321 and N 2322 – power supply and analogue display modules, feeding and displaying up to 2 or 6 amplifiers (±22 V, 0.3 or 1 A), with a ±10 V output on a BNC socket; 50 or 100 VA, about 3 and 3.5 kg [5]
• N 2323 – power supply and digital display module for up to 2 amplifiers: 4 digits and sign, ranges of 999.9 µm/m, 9999 µm/m and 99.99 mm/m, error up to 0.05%; up to 60 VA, about 4 kg [5]
• N 2332 – combined filter module, for measurements in the presence of interference: low-pass (8 Hz – 8 kHz), high-pass (2 Hz – 2 kHz) or band-pass (8 Hz – 2 kHz), with switched cut-off frequencies [5]
• N 2334 – module for positive, negative and maximum peak values, RMS and mean values of dynamic signals up to 20 kHz (crest factor up to 5), holding a peak with a time constant of 2000 s [5]
• N 2338 – calibration module for any configuration of the system, with calibration signals of 0.05 µV/V – 111 mV/V accurate to 0.05%, for bridges or half-bridges of 120, 360, 600 or 1000 Ω [5]
• N 2351 – balancing module for three measuring points (resistive ±2%, inductive ±10%), used with a switching unit to extend the number of points; up to 20 switchings per second [5]
• N 2362 – manual switching module, used with three N 2351 modules to connect 12 measuring points in turn to the amplifier, giving 4 or 8 V of preheating to the points not connected; several could be linked for more points [5]

The annex lists 17 configurations built from these modules, from the one-channel N 23/14.21 (analogue display) and N 23/14.23 (digital display) to the six-channel N 23/614.22, with versions adding the filter, calibration or peak, mean and RMS module, or switching and balancing of 12 measuring points (N 23/451.62, N 23/14.451.62.21 and N 23/14.451.62.23). Like IEMI’s own numbering above, it gives the calibration module as N 2338 and the switching module as N 2362, where the ICE list has an N 2336 calibration unit and an N 2352 switching unit [5].