Casio JP-100W is a digital wristwatch released in 1987, known as the first Casio model with a built-in pulse sensor. It used module 509 and offered timekeeping, alarms, stopwatch, timer, and a jogging pacer combined with a fingertip pulse check system. This made it one of Casio’s most futuristic experiments of the late 80s, often remembered today as a kind of “prototype smartwatch.”
Its direct successor was the Casio JP-200W, which featured a rounder case and a screw-back design for improved durability. A simpler sibling, the Casio JP-10, removed the electronic sensor and instead relied on manual pulse counting with a button. Together, these models formed Casio’s first generation of pulse-oriented sports watches aimed at runners and health-conscious users.
Casio JP-100W – Quick Technical Data
| Field | Data |
|---|---|
| Model | Casio JP-100W |
| Module | 509 |
| Battery | CR1616 |
| Manual | Casio Module 509 Manual (PDF) |
| Glass Type | Acrylic |
| Strap Size | 18 mm (lug) / 22 mm (case) |
| Case Material | Resin case with stainless steel press-fit back |
| Functions | Timekeeping, 3 alarms, hourly chime, 1/100 stopwatch with split memory, jogger stopwatch (pacer), countdown timer, pulse check |
| Production Years | 1987 – late 1980s |
What color versions of Casio JP-100W exist?
Casio JP-100W came in four main versions, all sharing the same black resin case and strap. The differences were in button colors, accent frames, and branding.
- Yellow Version
This version had a bright yellow “PULSE” button and matching accents on the case. It is the most visually striking and is generally considered the rarest among collectors.
- Blue with White Accents
This edition featured a blue “PULSE” button with white text highlights around the case.
- Blue with Yellow Accents
Here Casio combined a blue “PULSE” button with yellow highlights. This high-contrast design is popular among collectors, as it balances sporty looks with visibility.
- Timex Pulse Watch (White-Label Edition)
Timex sold this rebranded version under its own name. It was technically identical to the blue/yellow Casio version, featuring the same blue “PULSE” button and yellow accents. Because it was marketed separately, it has become a unique and rare variant in the JP-100W story.
👉 Collector note: The yellow version is the rarest, while the Timex edition is a curiosity highly valued by collectors who enjoy Casio white-label collaborations.
What features and functions does Casio JP-100W have?
Casio JP-100W combined everyday digital functions with training tools and a unique fingertip pulse sensor. It was aimed at joggers and health-conscious users who wanted more than just a basic sports watch.
- Timekeeping: 12/24h format, full calendar (manual correction needed for leap years).
- Alarms: 3 independent alarms (daily or weekly), hourly chime, and a 20-second alarm tone.
- Stopwatch: Runs up to 19 h 59 min 59.99 s, 1/100-second accuracy, memory for 9 split times.
- Jogger Stopwatch (Pacer): Adjustable tempo from 5–240 steps/min, sound alerts every 5 minutes, plus post-run reminders every 1 minute for 10 minutes to check pulse.
- Countdown Timer: Range from 1 second to 19 h 59 min 59 s, with auto-repeat.
Pulse Function
The pulsecheck sensor was the most innovative feature. It used an LED with photoelectric detection to read changes in blood flow in the fingertip.
- Shows pulse in BPM (beats per minute).
- Displays percentage of baseline pulse, set manually by the user.
- Stops automatically after 2–3 minutes if no input is detected.
- Designed to let runners compare resting vs. exercise pulse to control training intensity.
👉 At the time, this felt futuristic. Many users noted that results could vary depending on finger steadiness and light conditions, but it was still one of the earliest attempts at bringing health measurement into a wristwatch.
How easy is it to maintain Casio JP-100W today?
Casio JP-100W is fairly easy to keep wearable thanks to its replaceable strap, but restoring the sensor and cosmetic details can be difficult.
- Strap: The original resin strap (18 mm lug / 22 mm case) is fragile and cracks with age. Replacements fit without problem, so keeping the watch on the wrist is not an issue.
- Glass: The flat acrylic crystal scratches easily but can be polished with Polywatch or sanding, making it one of the easiest parts to restore.
- Pulse button: The colored paint on the “PULSE” button often fades or chips. Once it wears off, it is hard to bring back to original condition.
- Sensor frame: The thin aluminum frame around the sensor peels and rubs off. Over time it exposes the raw silver metal, which collectors often see as one of the biggest cosmetic issues of this model.
- Sensor function: If the sensor no longer works, sometimes the problem is a missing spring contact inside the module. The spring links the pulse button with the sensor circuit, and if it shifts or gets lost, the sensor will not activate. Repairing this requires carefully opening the module and adding or reseating the spring.
👉 In summary: the strap and glass are easy to fix, but the pulse button paint, aluminum sensor frame, and the sensor system itself are the hardest parts of maintaining a JP-100W today.
Casio JP-100W Manual
The Casio JP-100W runs on module 509. The original instruction manual explains all timekeeping, jogging, and pulse measurement modes.
📖 Casio JP-100W / Module 509 Manual (PDF)
Additional Information & Related Models
Casio positioned the JP-100W as part of its late 80s sports and health-oriented line. It was promoted as a runner’s watch with pulse-checking technology, something futuristic at the time.
- Casio JP-200W – direct successor with a rounder case, screw-back design, and a slightly more refined look.
- Casio JP-10 (Pulse Converter) – a simplified sibling that removed the LED sensor. Instead, users tapped a button in rhythm with their pulse to calculate heart rate manually.
- Timex Pulse Watch – white-label edition of the JP-100W sold under the Timex brand, visually identical to the blue/yellow version.
👉 Together, these models represent Casio’s first generation of pulse watches, a short-lived but fascinating experiment in wearable health tech long before smartwatches.
FAQ – Casio JP-100W
What battery does Casio JP-100W use?
Casio JP-100W uses a CR1616 lithium battery. Some users also report compatibility with CR1620 cells.
How rare is Casio JP-100W today?
It is considered rare and collectible, especially the yellow version and the Timex Pulse Watch white-label edition. Blue variants are more common but usually show heavy wear.
Does Casio JP-100W have a backlight?
No, this model does not include any illumination, which makes it harder to read in the dark.
How accurate was the pulse measurement on Casio JP-100W?
The pulse sensor worked, but accuracy depended on finger stability and lighting. Many users remember it as a novelty rather than a medical-grade tool.
Can I still find original straps for Casio JP-100W?
Original straps are almost impossible to find today. Collectors usually fit replacements, since the 18 mm lug size makes swapping straps relatively simple.
What are the weak points of Casio JP-100W?
The biggest issues are fading paint on the PULSE button, the peeling aluminum frame around the sensor, and sometimes a missing spring contact that prevents the pulse sensor from working.
Passionate about Casio’s golden-era digital watches. At Vintage Casio Restore, I bring old models back to life and share practical guides for collectors and enthusiasts.
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