Chat Live
Contact Us
sales@valuetronics.com
The Stanford Research Systems FS725 is a benchtop rubidium frequency standard that integrates a rubidium oscillator (SRS model PRS10), a low-noise AC power supply, and distribution amplifiers in a compact, half-width 2U chassis. It is built for stable, reliable long-term operation, with an estimated 20-year aging of less than 5 × 10⁻⁹ and a demonstrated rubidium oscillator MTBF of over 200,000 hours.
The FS725 is an ideal instrument for calibration and R&D laboratories, or any application requiring a precision frequency standard. It can be phase-locked to an external 1 pps reference such as GPS, providing Stratum 1 performance, making it suited to timing and synchronization tasks that demand a disciplined, traceable frequency source.
Every FS725 we offer is held in ValueTronics' own 20,000 square-foot secure warehouse at 1675 Cambridge Drive in Elgin, Illinois, where we stock and own the inventory we sell. Each pre-owned unit is inspected and functionally verified in-house by our technicians before it ships, while new units leave factory-sealed exactly as received from the manufacturer.
| Specification | Value |
|---|---|
| Output | |
| Output frequencies | 10 MHz sine, 5 MHz sine, 10 µs wide 1 pps pulse |
| Amplitude | 0.5 Vrms, ±10 % |
| 1 pps pulse amplitude | 2.5 V into 50 Ω, 5 V into High-Z loads |
| Phase noise (SSB) | <−130 dBc/Hz (10 Hz), <−140 dBc/Hz (100 Hz), <−150 dBc/Hz (1 kHz), <−155 dBc/Hz (10 kHz) |
| Spurious | <−100 dBc (100 kHz BW) |
| Harmonics | <−60 dBc |
| Accuracy at shipment | ±5 × 10⁻¹¹ |
| Aging (after 30 days) | <5 × 10⁻¹¹ (monthly), <5 × 10⁻¹⁰ (yearly), 5 × 10⁻⁹ (20 years, typ.) |
| Short-term stability (Allan variance) | <2 × 10⁻¹¹ (1 s), <1 × 10⁻¹¹ (10 s), <2 × 10⁻¹² (100 s) |
| Holdover | 72 hour Stratum 1 level (1 × 10⁻¹¹) |
| Frequency retrace | ±5 × 10⁻¹¹ (72 hrs. off, then 72 hrs. on) |
| Settability | <5 × 10⁻¹² |
| Trim range | ±2 × 10⁻⁹ (0 to 5 VDC), ±0.5 ppm (via RS-232) |
| Warm-up time | <6 minutes (time to lock), <7 minutes (time to 1 × 10⁻⁹) |
| Front-Panel Indicators (Green LEDs) | |
| Power | “On” when AC power is applied |
| Locked | “On” when frequency is locked to Rb |
| 1 pps input | Blinks with each 1 pps reference input applied to rear panel |
| 1 pps sync | “On” when 1 pps output is synchronized within ±1 µs of 1 pps input |
| Receive | Blinks when RS-232 characters are received by FS725 |
| Send | Blinks when RS-232 characters are sent by FS725 |
| Rear-Panel Connections | |
| Frequency adjust | 0 to 5 VDC adjusts frequency by ±0.002 ppm (normally unconnected) |
| 1 pps input | One 100 kΩ input. Requires CMOS level pulses (0 to 5 VDC). If an external 1 pps input is applied, lock is maintained between the 1 pps input and 1 pps output, with computer adjustable time constant from 8 minutes to 18 hours. |
| 10 MHz outputs | Two 50 Ω isolated sine outputs |
| 5 MHz output | One 50 Ω sine output |
| 1 pps output | One 50 Ω pulse output |
| Optional outputs | Each option board provides four 10 MHz, one 5 MHz, and one 1 pps outputs. Up to 3 boards can be installed. |
| Alarm relays | Max. current, 3 A. SPDT, normally open or normally closed. May be wired in parallel with other relays to “wire-or” a single alarm. |
| Rb lock | Relay status matches the front-panel “Locked” LED. |
| 1 pps | Relay status matches the front-panel “1 pps sync” LED. |
| RS-232 | 9-pin connector configured as DCE, 9600 baud. Windows RbMon software is provided. |
| Environmental | |
| Operating temperature | +10 °C to +40 °C |
| Temperature stability | ∆f/f < ±1 × 10⁻¹⁰ (+10 °C to +40 °C) |
| Storage temperature | –55 °C to +85 °C |
| Magnetic field | ∆f/f < 2 × 10⁻¹⁰ (1 Gauss field reversal) |
| Relative humidity | 95 % (non-condensing) |
| General | |
| AC power | 90 to 132 VAC or 175 to 264 VAC, 47 to 63 Hz, 50 W |
| Dimensions (W × H × L) | 8.5" × 3.5" × 13" |
| Weight | 9 lbs. |
| Warranty | One year parts and labor on defects in materials and workmanship |
Important: The rear-panel 1 pps input requires CMOS-level pulses (0 to 5 VDC) into its 100 kΩ input.
Recommended pairing: add Option 01, 02, or 03 distribution amplifier boards (6, 12, or 18 outputs) to expand the FS725's available 10 MHz, 5 MHz, and 1 pps output count.
This pre-owned unit is inspected and functionally verified in-house before it ships and is backed by our pre-owned warranty. To confirm its exact condition, firmware revision, installed options, or included accessories for your application before ordering, contact our Test Architects.
ValueTronics supplies both new and used test and measurement equipment. New units ship factory-sealed, exactly as received from the manufacturer; every used unit is inspected and functionally verified in-house at our 20,000 sq ft secure facility in Elgin, Illinois before it ships. Our Test Architects can help you select the condition, calibration, and configuration that fit your application.
Please review the Manufacturer's Data Sheet to verify published specifications. Feedback on this webpage is always welcome — please reach out to your Test Architect at any time for questions or concerns. Thank you, we truly appreciate you being our customer.
Model No
Stanford
Condition
Pre-Owned
Manufacturer
Stanford Research Systems
30+ Years in Business
Secure Payments
Sell Test Equipments
Knowledgeable Staff
On-site Lab
30+ Years in Business
Secure Payments
Sell Test Equipments
Knowledgeable Staff
On-site Lab
Request A Quote
