The SC-7101/SC-7102 are compact and lightweight electronic frequency counters designed for measuring frequencies from 10 Hz to 200 MHz. They feature a large, high-luminosity LED display for easy readability and incorporate several advanced features for enhanced measurement capabilities and user convenience.
Function Description:
The primary function of these instruments is frequency measurement. They are capable of measuring low-frequency signals with high resolution using a reciprocal method, which allows for 7-digit resolution per 1 second in a very limited time. For input signals of 10 MHz or more, the instrument automatically switches to direct frequency measurement to achieve the highest possible resolution.
A notable feature is the DIFF calculation function, which allows the user to calculate and display the difference between an input signal's value and a stored reference value with a simple operation. This is particularly useful for comparative measurements.
The counters are designed for easy system integration, offering optional GP-IB or Centronix type parallel interfaces. These interfaces enable the output of measured results, external reset capabilities, and remote control of the time base, allowing the instrument to be incorporated into larger measurement systems.
Both models include a built-in highly stabilized reference oscillator. The SC-7101 has an oscillator with an aging rate of ±3 x 10⁻⁷/month and ±10 x 10⁻⁷/year, while the SC-7102 features an even more stable oscillator with an aging rate of ±2 x 10⁻⁸/day and ±10 x 10⁻⁸/year. Additionally, the instruments support external input of highly accurate reference signals for even greater precision.
The SC-7102 model offers a 4-step setting for the sample rate, allowing users to select between 200 msec x 1, x 2, x 4, and x 8.
The instruments are housed in specially treated lightweight plastic cases that provide improved shielding effects, comparable to or better than metal cases.
Important Technical Specifications:
Frequency Measurement:
- Measuring Range:
- 10 Hz to 200 MHz
- 1 kHz to 200 MHz with time base of 1 ms (SC-7102 only)
- 100 Hz to 200 MHz with time base of 10 ms
- Input Voltage:
- At ATTEN 1: 20 mVrms to 1 Vrms (1 kHz to 100 MHz); 50 mVrms to 1 Vrms (10 Hz to 200 MHz)
- At ATTEN 1/20: 0.4 Vrms to 20 Vrms (1 kHz to 100 MHz); 1 Vrms to 20 Vrms (10 Hz to 200 MHz)
- Maximum Input Voltage: 200 V (DC + peak AC)
- Input RC: Approximately 1 MΩ/25 pF or less
- Attenuator: 1 or 1/20
- Input Coupling: AC
- Time Base:
- SC-7101: 10 ms, 0.1 s, 1 s, 10 s
- SC-7102: 1 ms, 10 ms, 0.1 s, 1 s, 10 s
- Resolution:
- 10 MHz or more:
- SC-7101: 100 Hz/10 ms, 10 Hz/0.1 s, 1 Hz/1 s, 0.1 Hz/10 s
- SC-7102: 1 kHz/1 ms, 100 Hz/10 ms, 10 Hz/0.1 s, 1 Hz/1 s, 0.1 Hz/10 s
- 10 MHz or less:
- SC-7101: 5 digits/10 ms, 6 digits/0.1 s, 7 digits/1 s, 8 digits/10 s
- SC-7102: 4 digits/1 ms, 5 digits/10 ms, 6 digits/0.1 s, 7 digits/1 s, 8 digits/10 s
- Reading Unit: EXPONENT (0, ±3, ±6, ±9) Hz
- Error:
- 10 MHz or more: Accuracy of reference oscillator ± 1 count
- 10 MHz or less: Accuracy of reference oscillator + (Trigger error ± 1 reference time) / (Measured frequency x Time base)
General Specifications:
- Calculating Function: DIFF (X-Xref), where X is the measured value and Xref is the reference value.
- Display Method: Storage display using light-emitting diodes, zero blanking method.
- Display Digits: Decimal 9 digits for mantissa (or 8 digits with a negative sign for DIFF calculation), 1 digit for exponent (0, ±3, ±6, ±9).
- Display Time: Time base + sample rate or infinite display.
- Sample Rate:
- SC-7101: Approximately 200 ms
- SC-7102: Approximately 200 ms, 400 ms, 800 ms, or 1.6 s
- Reference Oscillator:
- Oscillation Frequency: 10 MHz
- Aging Rate:
- SC-7101: ±3 x 10⁻⁷/month, ±10 x 10⁻⁷/year (on the basis of 1 hour after power on)
- SC-7102: ±2 x 10⁻⁸/day, ±10 x 10⁻⁸/year (on the basis of 24 hours after power on)
- Rise Time:
- SC-7101: ±3 x 10⁻⁶ (on the basis of 1 hour after power on, from immediately after power on)
- SC-7102: ±5 x 10⁻⁸ (on the basis of 1 hour after power on, from 10 minutes after power on)
- Temperature Variation:
- SC-7101: ±3 x 10⁻⁶/0 °C to +40 °C
- SC-7102: ±5 x 10⁻⁸/0 °C to +40 °C
- Vibration:
- SC-7101: ±1 x 10⁻⁷ or less (for 30 minutes each in three directions at frequency of 10 Hz to 55 Hz and with amplitude of 1.5 mm)
- SC-7102: ±5 x 10⁻⁸ or less (for 30 minutes each in three directions at frequency of 10 Hz to 55 Hz and with amplitude of 1.5 mm)
- Impact:
- SC-7101: ±1 x 10⁻⁷ or less (dropping from height of 50 mm above a hard wood three times each in three directions)
- SC-7102: ±5 x 10⁻⁸ or less (dropping from height of 50 mm above a hard wood three times each in three directions)
- Output of Reference Frequency:
- Frequency: 10 MHz
- Released Voltage: 2 Vp-p or more (350 mVp-p or more into 50 Ω terminal)
- Input of Reference Frequency:
- Frequency: 10 MHz
- Input Voltage: 1 Vrms to 5 Vrms
- Maximum Input Voltage: 10 Vrms
- Input Resistance: Approximately 10 kΩ
- Input Coupling: AC
- Power Supply:
- Supply Voltage (selectable via plug):
- AC 100 V (range 90 to 110 V)
- AC 120 V (range 108 to 132 V)
- AC 220 V (range 198 to 242 V)
- AC 240 V (range 216 to 264 V)
- Frequency Range: 50 Hz to 400 Hz
- Power Consumption: Approximately 11 W (SC-7101), Approximately 15 W (SC-7102)
- Physical Characteristics:
- Weight: Approximately 2.5 kg
- Dimension: (210±2)W x (100±2)H x (310±2)L [mm]
- Environmental Characteristics:
- Operating Temperature: 0 °C to +40 °C
- Operating Humidity: 85 %RH or less (0 °C to +40 °C)
- Storage Temperature: -20 °C to +70 °C
- Storage Humidity: 90 %RH or less (0 °C to +70 °C)
Usage Features:
- Easy-to-Read Display: The 9-digit decimal LED display with an additional exponent digit uses a zero-blanking method for clear readings.
- Front Panel Controls:
- POWER ON-OFF: Controls the line voltage.
- Numerical Display LED: Shows measured results and exponent.
- STATUS LED: Indicates operating status (REMOTE, OVER, GATE, OVEN for SC-7102).
- BNC Connector (INPUT): For signal input (10 Hz to 200 MHz).
- FILT NORM-10 kHz: Selects a 10 kHz low-pass filter to attenuate high-frequency noise in low-frequency signals.
- ATTEN 1/20-1: Selects input attenuator (x1 or x20).
- TIME BASE: Selects measurement gate time (1 ms, 10 ms, 0.1 s, 1 s, 10 s).
- CHECK: Toggles between "check" mode (self-check with internal 10 MHz reference oscillator) and "measure" mode (measures input signals).
- DIFF: Activates DIFF calculation (X-Xref).
- HOLD: Toggles between "hold" mode (stops measurement and displays current results) and "sample" mode (repeats measurements).
- RESET (LOCAL): Interrupts processes, clears display, updates measurements, registers Xref in DIFF mode, and acts as a LOCAL key in GP-IB mode.
- SAMPLE RATE x2, x4, x8 (SC-7102 only): Selects sample rate time (200 ms, 400 ms, 800 ms, 1.6 s).
- Rear Panel Controls:
- 10 MHz STD IN-OUT BNC connector: Provides 10 MHz from the internal reference oscillator (OUT) or accepts external reference signals (IN).
- FUSE, VOLTAGE SELECTOR: Contains the fuse holder and power supply voltage selector plug.
- AC LINE INPUT: For connecting the power cord.
- GND Terminal: Protective grounding terminal.
- Optional Connector Locations: Data Out (SC-0108 parallel interface), REMOTE (SC-0110 GP-IB interface), and corresponding switch locations.
- Display Hysteresis: For low-frequency measurements (10 MHz or less), the display intelligently shifts to the left or right and blanks the lowest digit when the MSD value changes from 9 to 10 or 10 to 9, ensuring stable and easy readability. This process is performed without such operations if the MSD value is between 2 and 8.
- Carrying Handle/Stand: The handle can be pulled outward at both ends to release its lock, allowing it to turn approximately every 20 degrees. When fixed at the bottom of the instrument, it serves as a stand. For storage, it can be turned to the rear side of the instrument.
- Secondary Frequency Standard: When the IN-OUT switch on the rear panel is set to "OUT", the 10 MHz STD connector provides a 10 MHz reference oscillator signal, which can be used as an external driving signal for pulse generators or time markers for adjusting oscilloscopes due to its high accuracy.
Maintenance Features:
- Voltage Selector: The instrument's operating voltage can be selected via a plug on the rear panel. Users must ensure the correct voltage is selected to prevent damage.
- Fuse Replacement: A 0.3 A fuse is used to protect the circuit from excessive voltage. If the fuse blows, it must be replaced with one of the same rated current after identifying and repairing the cause of the fault.
- Reference Oscillator Adjustment: The manual provides procedures for adjusting the internal crystal oscillator to maintain high accuracy, especially for continuous high-accuracy measurements. This involves removing the upper cover and performing adjustments under specific environmental conditions (ambient temperature of +23°C ± 5°C and humidity of 85%RH or less) after a minimum 1-hour warm-up period.
- External Reference Oscillator Connection: For even higher accuracy, an external reference oscillator can be connected to the 10 MHz STD IN-OUT BNC connector, provided the rear panel switch is set to "IN".
- Cautions on Operations: The manual outlines important cautions, including operating within specified ambient temperatures (0°C to +40°C), ensuring proper ventilation, checking supply voltage, avoiding excessive input voltage (max 200 V DC + peak AC), using supplied coaxial cables for input signals to prevent noise, and ensuring proper grounding of the protective ground terminal.
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