The HM1-UD connects your PC to HART field instruments so device-management software can configure, calibrate and diagnose them. No power supply is required — the modem is powered from the USB port.
Getting started
- Connect the modem to a USB port on your PC — directly, or using a USB extension lead. It is powered from the USB port; no supply is needed.
- Install the driver. On an internet-connected Windows PC the USB driver normally installs automatically the first time the modem is connected. If it does not, install the driver supplied with the product or download it from the support site. The driver creates a virtual serial (COM) port your HART software will use.
- Find the COM port. Open Windows Device Manager → Ports (COM & LPT) and note the COM number assigned to the modem (for example COM4).
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Connect to the HART loop. Clip the two flying leads across the HART device or an appropriate loop load resistance. The connection is polarity-independent (either lead to either terminal) and the loop interface is fully isolated from your PC.
• A HART signal needs a loop load of roughly 250 Ω. On a live 4–20 mA loop this is usually already present; on the bench, add a suitable resistor.
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Open your device-management software — PACTware, FieldCare, FieldMate, SIMATIC PDM or another DTM/DD-based tool — and point its HART communication driver at the modem's COM port.
• HART uses standard serial settings of 1200 baud, 8 data bits, odd parity, 1 stop bit (8-O-1). Most tools apply these automatically.
- Scan for devices. Start a HART scan or connect in your software. Use polling address 0 for a single point-to-point device, or 1–15 for a multi-dropped loop.
- Documentation. Full specifications are in the product datasheet, available from support.lawnswoodtechnology.com.
- For further assistance, raise a support ticket at support.lawnswoodtechnology.com. Quote the model HM1-UD and the software you are using.
Troubleshooting
Modem not shown in Device Manager
Driver not installed — install it and reconnect, or try another USB port or lead.
Software cannot find the device
Check the COM-port number, the 8-O-1 serial settings, and the flying-lead connection to the loop.
No response / intermittent communication
Confirm a loop load of about 250 Ω is present and keep the leads clear of noise sources.
Multi-drop device not found
Scan polling addresses 1–15; devices on a multi-dropped loop are not at address 0.
Compatible with PACTware, FieldCare, FieldMate, SIMATIC PDM and other DTM/DD-based device-management tools.