1.2 GHz and 520 MHz Counters

• 5 Hz to 1.2 GHz range on 1855
• 5 Hz to 520 MHz range on 1851
• Frequency, period, period average, and totalize functions
• Selectable resolution
• 8 digit LED display
• Low pass filter
• Display hold
• Switchable X1/X10 attenuator
• Remote start-stop
• 1 PPM TCXO Time Base Accuracy

520 MHz Model 1851

1.2 MHz Model 1855

SPECIFICATIONS:(Common to each model except as noted)
FREQUENCY CHARACTERISTICS
Range Channel A: kHz Mode: 5 Hz to 5 MHz sine wave. MHz Mode: 5 Hz to 80 MHz sine wave.
Model 1855 Prescale: 75 MHz to 1.2 GHz sine wave.
Model 1851 Prescale: 10 MHz to 520 MHz sine wave.
Accuracy: +Time base accuracy, +1 count.
RESOLUTION
Channel A, kHz Mode: 0.1 Hz to 100 Hz, switch selectable in four decade steps.
Channel A, MHz Mode: 1 Hz to 1000 Hz, switch selectable in four decade steps.
Prescale: 10 Hz to 10 kHz, switch selectable in four decade steps.
Display: kHz or MHz with decimal point.
PERIOD CHARACTERISTICS
Range: 0.5 muis to 200,000 muis.
Frequency Range: 5 Hz to 2 MHz sine wave.
Accuracy: ± count ±time base error ±trigger error.*
Resolution: 100 ps to 100 ns, switch selectable in four decade steps.
Display: µs with decimal point.
Minimum Pulse Width: 250 ns.
TOTALIZE CHARACTERISTICS
Range: 5 Hz to 15 MHz sine wave.
Capacity: 0 to 99,999,999 plus overflow LED.
Control: Manual reset and hold from the front panel.Normally enabled, except when signal
at back panel START/STOP jack is low.
INPUT CHARACTERISTICS
Channel A
Bandwidth: 5 Hz to 80 MHz
Sensitivity: 30 mVrms, 5 Hz to 30 MHz
50 mVrms, above 30 MHz
Impedance: 1 Mohm (<40 pF)
Attenuator: X1/X10, switch selectable
Coupling: ACFilter: 100 kHz, - 3 dB, switch selectable
Connector: BNC on front panel
Maximum Input:
200 V (peak AC + DC) DC to 500 Hz, decreasing
linearly to 100 V (peak AC + DC) at 1 kHz. 100 V
(peak AC + DC) 1 kHz to 5 MHz, decreasing linearly
to 20 V (peak AC + DC) at 80 MHz.
PRESCALE Model 1855
Bandwidth: 75 MHz to 1.2 GHz
Sensitivity: 25 mVrms, 75 MHz to 1.0 GHz 50 mVrms, 1.0 GHz to 1.2 GHz
PRESCALE Model 1851
Bandwidth: 10 MHz to 520 MHz
Sensitivity: 50 mVrms, 10 MHz to 520 MHz
Impedance: 50 ohms
Coupling: AC
Connector: BNC on front panel
Maximum Input: 5 Vrms
TOTALIZE START/STOP INPUT CHARACTERISTICS
Logic Levels: Standard TTL levels; low level inhibits totalizing, high level enables it.
Loading: One standard TTL gate.
TIME BASE CHARACTERISTICS
Standard Type: TCXO (temperature compensated crystal oscillator).
Frequency: 10 MHz.
Setability: +0.1 ppm (+1 Hz).
Line Voltage Stability: Less than ±0.1 ppm with ±10% line voltage variation.
Temperature Stability: Less than ±.0001% (±1ppm from OºC to 50ºC ambient).
Maximum Aging Rate: ± ppm/year.
DISPLAY CHARACTERISTICS
8 LED's: 0.43" seven segment digits
LED Indicators: for kHz, MHz, p,SEC, GATE, and OVERf low indicators.
Display Update Time:
kHz and MHz FREQUENCY Mode: User selected
gate time plus fixed 200 ms interval.
Pre-Scale Mode: User selected gate time plus fixed 200 ms interval.
PERiod Mode: User selected cycles averaging plus fixed 200 ms interval.
TOTALize Mode: Continuous.
GENERAL
Power Requirements: Universal, AC, 100 V, 120 V, 220 V, 240 V, (all ±10%), 50/60 Hz, 21 W,
set by internal PC jumpers.
Dimensions (HxWxD): 3.75" x 9.5" x 12.6" (9.5 cm x 24 cm x 32 cm)
Weight: Model 1855 2.47 kg (5.44 lbs.);
Model 1851 2.41 kg (5.31 lbs.)
ACCESSORIES SUPPLIED
Instruction manual, schematic diagram and parts list.
OPTIONAL ACCESSORIES
Deluxe 10:1/Direct Probe PR-37
Deluxe X10 Probe PR-45

*NOTE: Trigger error is typically ±0.3% of reading divided by the number of cycles averaged,
for input signals having better than 40 dB S/N ratio and greater than 100 mV amplitude.

B&.K-PRECISION counters provide the versatility and reliability required for a broad spectrum of
laboratory and service applications.In addition to frequency measurement, most B&K-PRECISION
counters also provide period and totalize measurement capabilities.Each counter is built for
continued high accuracy over a wide range of operating conditions. Each unit features bright
LED B&.K-PRECISION counters provide the versatility and reliability required for a broad
spectrum of laboratory and service applications. In addition to frequency measurement,most
B&K-PRECISION counters also provide period and totalize measurement capabilities. Each
counter is built for continued high accuracy over a wide range of operating conditions.
Each unit features bright LED